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STRUCTURAL  DESIGN 


VOLUME    I 
ELEMENTS  OF  STRUCTURAL  DESIGN 


BY 

HORACE  R.  THAYER 

ASSISTANT  PROFESSOR  OF  STRUCTURAL  DESIGN 

CARNEGIE  TECHNICAL  SCHOOLS 

PITTSBURG,  PA. 


NEW  YORK 

D.    VAN    NOSTRAND    COMPANY 

TWENTY-FIVE    PARK    PLACE 
1912 


COPYRIGHT,    1912 

BY 
D.  VAN  NOSTRAND  COMPANY 


THE    SCIENTIFIC    PRESS 

ROBERT     DRUMMOND     AND    COMPANY 

BROOKLYN,     N.    Y. 


PREFACE 


IT  might  be  well  to  say  here  what  is  repeated  in  the  text: 
that  this  work  presupposes  a  knowledge  of  mechanics,  stresses, 
and  the  mathematics  on  which  they  depend. 

The  experience  of  the  author  in  teaching  and  in  practice 
has  led  him  to  believe  that  no  available  book  presents  all 
structural  subjects  so  concisely  that  they  can  be  covered  in 
the  time  usually  allotted  by  technical  schools.  Moreover, 
the  fundamental  principles  of  shop  practice  and  erection,  which 
govern  the  designer  at  every  step,  are  not  clearly  developed. 
These  faults  the  author  has  attempted  to  correct,  using  only 
orthodox  methods  of  presentation. 

This  volume  considers  wooden  structures  and  the  fundamental 
principles  of  design  in  steel.  Should  this  work  receive  recognition, 
it  is  intended  to  follow  it  by  a  second  volume  on  the  "  Design 
of  Simple  Structures,"  plate  girders,  viaducts,  truss  bridges, 
mill  buildings,  high  office  buildings,  and  standpipes,  and  a 
third  on  the  "Design  of  Advanced  Structures,"  cantilever, 
movable,  and  suspension  bridges  and  arches.  It  has  been 
thought  best  for  the  present  to  omit  the  data  usually  found  in 
handbooks. 

As  a  considerable  portion  of  this  treatise  is  original  data, 
corrections  and  suggestions  will  be  especially  welcome.  How- 
ever, a  great  deal  of  pains  has  been  taken  to  eliminate  errors. 

The  writer  wishes  at  this  time  to  acknowledge  his  references. 
These  include  almost  every  American  authority  on  the  subject. 
Many  of  them  have  been  referred  to  at  the  proper  place  in  the 
book.  Particular  mention  should  be  made  of  the  Engineering 
News,  Engineering  Record,  and  Transactions  of  the  American 
Society  of  Civil  Engineers.  The  last  two  kindly  allowed  the 

iii 

261193 


iv  PKEFACE 

reproduction  of  their  illustrations.    The  aid  rendered  by  various 
manufacturers  is  acknowledged  in  the  text. 

The  author  desires  to  thank  the  following  gentlemen  for 
assistance  in  revising  manuscript:  Registrar  Tarbell  and  Profs. 
McCullough,  Jones,  Lose,  and  H.  S.  Dornberger  of  the  Carnegie 
Technical  Schools  and  Messrs.  Gordon,  Allen,  and  R.  S.  Dorn- 
berger. H.  R.  T. 

CARNEGIE  TECHNICAL  SCHOOLS, 
PITTSBURGH,  Pa.,  March  15,  1912. 


CONTENTS 


CHAPTER  I 

MATERIALS 

ART.  PAG2 

1.  Introduction i 

2.  Growth  and  Characteristics  of  Timber ; 2 

3.  Faults  of  Timber 5 

4.  Preservative  Processes  for  Timber 8 

5.  Varieties  of  Timber '. 10 

6.  Strength  of  Timber 1 1 

7.  Uses  of  Timber 13 

8.  Cast  Iron 13 

9.  \Yrought  Iron 15 

10.  Bessemer  Steel 16 

1 1 .  Open  Hearth  Steel 17 

12.  Cast  Steel  and  Alloys  of  Steel .  .' 19 

13.  Paints 20 


CHAPTER  II 

COMMERCIAL  SHAPES 

14.  Handbooks  Units  and  Dimensions 22 

15.  Commercial  Shapes  of  Wood 24 

16.  Commercial  Shapes  for  Cast  Iron  and  Steel  Castings 25 

1 7.  Rolling 27 

18.  Circular  Shapes 29 

19.  Rectangular  Shapes 3° 

20.  Angles 3r 

21.  I-Beams  and  Channels 33 

22.  Occasional  Shapes 34- 

23.  Rare  Shapes 36 

v 


vi  CONTENTS 


CHAPTER  III 

WOODEN  STRUCTURES 

ART.  PAGE 

24.  Principles  of  Design 37 

25.  Accessories  of  Other  Material 40 

26.  Joints 42 

27.  Designs  of  Timber  Structures 51 

28.  General  Description  of  Roof  Trusses 54 

29.  Computations  for  a  Roof  Truss 57 

30.  Trussed  Beams 62 

31.  Description  of  Bridges 67 

32.  Computations  for  a  Bridge 69 

33.  Trestle  Bents 75 


CHAPTER  IV 

FABRICATION  OF  STRUCTURAL  STEEL 

34.  Organization  of  Administration 79 

35.  Plant  in  General 80 

36.  Stock  Yard 83 

37.  Main  Shop 85 

38.  Machine  Shop 95 

39.  Forge  Shop 98 

40.  Templets 100 

41.  Methods  of  Cutting  Material 102 

42.  Methods  of  Bending 104 

43.  Process  for  Upsetting 106 

44.  Methods  for  Making  Holes 108 

45.  Layout  and  Assembly 109 

46.  Fastenings  for  Steel  Work no 

47.  Methods  for  Riveting 113 

48.  Inspection  Painting  and  Shipment 117 

49.  Erection 119 

CHAPTER  V 

THE  ENGINEERING  DEPARTMENT 

50.  Specifications 131 

51.  Problem  of  Design 140 

52.  Economical  Relations 143 

53.  Estimating 146 


CONTENTS  vii 

ART.  PAGE 

54.  Design  of  Beams 148 

55.  Design  of  Tension  Members 157 

56.  Design  of  Compression  Members 161 

57.  Strain  Sheet 172 

58.  Detailing 172 

59.  Design  of  Splices  and  Beam  Connections 179 

60.  Design  of  Riveted  and  Pin  Joints  in  Trusses 183 

61.  Shoes 186 

62.  Structural  Drawings 193 

63.  Auxiliaries — Bills  of  Materials 198 

64.  Bills  of  Eyebars,  Pins  and  Accessories 201 

65.  Other  Bills 203 

66.  Checking 204 

67.  Other  Steps 207 

68.  Examination  of  Structures  in  Use 208 

69.  Failures 209 


ELEMENTS  OF  STRUCTURAL  DESIGN 


CHAPTER  I 

MATERIALS 
Art.  i.    Introduction 

THIS  work  is  intended  for  students  and  draftsmen  who 
understand  analytical  mechanics,  mechanics  of  materials,  and 
methods  of  determining  stresses  either  by  graphics  or  by  com- 
putation. On  this  account,  only  a  synopsis  of  results  will  be 
given  in  sample  designs.  However,  the  reader  should  check 
each  operation  to  be  sure  that  he  thoroughly  understands  it. 

The  writer  believes  that  the  difficulty  usually  found  in  teach- 
ing structural  work  arises  from  the  fact  that  fundamental 
principles  are  not  clearly  developed  and  illustrated  by  simple 
examples  at  the  start.  It  is  axiomatic  among  practical  men 
that  a  thorough  knowledge  of  details  should  precede  any  attempt 
at  design.  Yet  this  well  established  principle  is  often  ignored 
in  technical  training. 

We  shall  consider  first  the  materials  and  their  commercial 
shapes,  which,  often  altered  in  manufacture,  are  used  in  struc- 
tural work;  next,  the  organization  of  companies  to  handle 
them;  afterwards,  their  machines,  their  capacities,  and  the  way 
in  which  they  operate  to  transform  the  original  shapes;  then  the 
means  by  which  a  member  carrying  a  given  stress  can  be  rrost 
economically  fabricated  to  carry  its  load;  next  the  methods 
of  fastening  together  these  different  members;  and  finally, 
the  design  of  the  finished  structures. 

In  order  to  serve  as  a  reference  book  for  the  student  and 
draftsman,  much  data  will  be  given  which  will  be  supplanted 
in  practice  by  the  slightly  different  standards  of  the  locality  or 


2  ELEMENTS  OF  STRUCTUKAL  DESIGN 

of  the  company  concerned.  For  example,  the  common  sizes 
of  timber  as  given  in  Art.  15,  vary  somewhat  with  the  locality 
and  date.  They  are  inserted,  however,  to  give  an  idea  about  how 
they  run,  to  serve  as  a  standard  for  student  designs,  and  to  be 
used  where  other  information  is  not  available.  Data  of  this 
sort  should  not  be  memorized. 

Art.  2.    Growth  and  Characteristics  of  Timber  * 

The  advantages  of  timber  are  that  it  is  light,  cheap,  abundant, 
and  easily  worked  or  altered.  On  the  other  hand,  it  is  accessible 
to  vermin  and  insects,  is  combustible,  quite  perishable,  and 
weak  in  shear  and  bearing  perpendicular  to  the  grain.  These 
weaknesses  are  more  fully  discussed  in  Chapter  III.  The 
approaching  exhaustion  of  our  reserve  supplies  has  partially 
neutralized  its  advantages  of  abundance  and  cheapness. 

Timber  is  cut  from  the  trees  in  a  manner  familiar  to  all. 
Those  woods  which  are  used  in  construction  are  almost  entirely 
exogenous.  These  grow  by  formation  of  new  wood  each  year 
on  the  outer  surface.  On  a  transverse  section  of  the  tree,  they 
appear  as  rings  whose  number  equals  its  age  in  years.  Each 
ring  is  composed  of  two  parts:  an  inner  portion  called  spring 
wood  which  is  soft  and  lacking  in  strength;  and  an  outer  part 
called  summer  wood  which  is  hard  and  strong.  Hence  the 
more  of  the  latter,  the  stronger  the  timber  is.  In  the  conifers 
(pine,  spruce,  and  hemlock),  the  summer  wood  is  dark  and  the 
spring  wood  light;  in  the  broad  leaved  trees  (oak,  maple,  birch), 
the  reverse  is  true.  When  these  annual  rings  are  narrow,  wood 
is  said  to  be  fine  grained;  if  wide,  coarse  grained.  When  fibers 
are  not  parallel  to  axis,  as  in  hemlock,  it  is  called  cross-grained; 
when  wavy  as  in  maple,  wavy  grained  or  curly.  The  figuring 
of  bird's-eye  maple  is  due  to  the  concentric  circles  appearing  in 
a  tangential  section  of  unevenly  growing  wood. 

A  zone  of  the  wood  next  to  the  bark  and  i  to  3  inches  wide  is 
lighter  than  the  remainder  and  is  termed  sapwood  because  it  is 

*  References  for  Timber:  Bulletin  No.  10,  U.  S.  Forestry  Div.,  Agricultural 
Department,  1895;  Johnson's  "Materials  of  Construction";  Kidder's  "  Building 
Construction  and  Superintendence,"  Part  II.  Snow's  "  Principal  Species  of 
Wood." 


MATERIALS  3 

active  in  carrying  the  sap.  The  interior  of  the  tree  called 
heartwood  is  inert  and  fulfills  only  the  mechanical  function  of 
helping  to  sustain  the  tree.  Sapwood  is  weak  and  subject  to 
rapid  decay  owing  to  the  great  amount  of  fermentable  matter 
contained  therein. 

Outside  of  the  tree  is  the  bark,  a  rough  scaly  covering  whose 
appearance  is  often  of  assistance  in  determining  species.  In 
preparing  the  tree  for  use  as  lumber,  the  bark  should  be  sawn  or 
stripped  off,  as  it  interferes  with  seasoning. 

Inside  of  the  bark,  sap  and  heartwood,  spring  and  summer 
wood  alike,  is  made  up  of  "  wood  fibers  "  and  "  medullary  " 
or  "  pith "  rays.  The  former  are  small  hollow  cells  about 
o.i  inch  long  and  .001  inch  in  diameter.  Their  greatest  length 
is  ordinarily  parallel  to  the  axis  of  the  tree.  Pith  rays  are 
somewhat  similar  but  smaller  cells,  extending  radially.  Much 
the  greater  part  of  the  timber  is  composed  of  wood  fibers  and  this 
gives  rise  to  some  of  its  structural  peculiarities. 

In  the  first  place,  as  we  should  expect,  its  principal  strength 
lies  in  a  direction  parallel  to  the  axis  of  the  tree.  Other  ways 
it  is  weak,  as  in  shearing  along  the  grain  or  in  bearing  per- 
pendicular to  the  grain. 

The  shrinkage  of  timber  is  also  affected  by  this  peculiar 
composition.  Roughly,  green  timber  is  one-half  water;  2  per 
cent  is  a  constituent  part  of  the  cells  of  the  sap  wood;  18  per  cent 
saturates  the  walls  of  all  cells;  the  remaining  30  per  cent  fills 
the  cavities.  All  but  a  small  part  of  this  moisture  may  be 
expelled  by  drying.  However,  on  exposure  to  the  air,  dried 
lumber  takes  up  moisture  until  a  10  to  15  per  cent  content  is 
reached.  This  is  the  standard  for  seasoned  lumber. 

There  are  three  reasons  for  seasoning.  First,  to  increase 
its  strength  (Art.  6).  Next,  the  large  amount  of  water  and  sap 
in  green  stuff  affords  a  favorable  condition  for  the  growth  of 
those  germs  which  cause  decay  (Art.  3).  Finally,  the  removal 
of  moisture  as  it  dries  out,  alters  the  dimensions  of  the  timber. 
Let  us  study  this  change  with  care. 

As  one  might  expect,  the  relative  change  in  the  direction  of 
the  main  axis  of  the  cells  is  small;  perpendicular  to  said  axis,  it  is 
large.  Radially,  Fig.  20 ,  it  is  held  in  a  measure  by  the  pith 
rays.  Tangentially  there  is  no  restriant  and  more  of  the  shrink- 


4  ELEMENTS  OF  STRUCTURAL  DESIGN 

age  takes  place  in  this  direction.  For  this  reason,  green  lumber 
of  the  shapes  seen  in  Fig.  2b,  takes,  after  seasoning,  forms 
exaggerated  in  Fig.  2C.  The  longitudinal  shrinkage  of  timber 
will  average  about  one  one-thousandth  of  the  length.  Approx- 


FIG.  2&. — Original  Shapes — Green. 


FIG.  2a. — Tangential  and  Radial.     FIG.  20. — Resulting  Forms — Seasoned. 


imate  values  of  radial  and  tangential  shrinkage,  deduced  from 
U.  S.  Timber  Tests,  follow: 


Variety. 

Radial. 

Tangential. 

» 
Soft  pine  cedar  cypress  spruce 

O2O 

OA. 

Hard  pine  

.02^ 

oct; 

Ash,  elm  poplar  walnut,  maple    

O^O 

O7O 

Chestnut 

O4.O 

080 

Oak 

060 

I  20 

There,  are  two  miethods  of  seasoning:  (a)  Air,  (b)  kiln 
drying.  In  the  former,  the  lumber  is  stacked  in  the  open  and, 
as  far  as  possible,  arranged  to  shed  water  yet  give  the  air  free 
access.  This  usually  takes  from  two  to  three  years  and  the 
lumber  is  never  fit  for  some  purposes.  A  kiln  is  a  tight  chamber 
through  which  a  current  of  air  of  about  150  to  180°  F.  is  passed. 
Hard  woods  should  first  be  air-dried.  Steaming  is  often  employed 
to  prevent  checking  or  case  hardening  (see  next 
article) .  Four  to  six  days  are  required  for  i  inch 
material  and  longer  for  larger  stuff. 

At  the  junction  of  the  limb  and  stem,  fibers 
on  the  lower  side  run  into  trunk  as  seen  in  Fig.  2d. 
On   upper  side  fibers  are   not   continuous.      For 
this  reason  a  split  made  above  does  not  run  into 
the  knot,  while  one  made  below  does.     When  limbs  die,  they 


FIG.  id. — Grain 
at  a  Knot. 


MATERIALS  5 

break  off,  and  are  finally  covered  by  the  growth  of  the  trunk, 
and  give  rise  to  the  annoying  dead  or  loose  knots.  Their 
weakening  effect  is  fully  explained  by  the  structure  of  the  timber 
at  this  point. 

The  color  of  the  timber  serves  as  a  characteristic  mark 
for  many  species,  is  a  help  in  detecting  decay,  and  adds  to  the 
appearance  of  certain  finishing  woods.  Odor  is  of  importance 
for  the  first  two  reasons.  Cypress  and  hard  pine,  much  alike 
in  appearance,  may  be  distinguished  by  the  resinous  odor  of  the 
latter.  Resonance  is  that  property  which  enables  a  substance 
to  transmit  sound.  In  timber,  knots  and  other  irregularities 
lessen  this  transmission.  Decaying  wood  gives  a  dull  heavy 
sound  when  struck  with  a  hammer. 

Values  for  the  weight  of  various  kinds  of  wood  in  pounds  per 
cubic  foot  are  as  follows: 


Variety. 

Weight,  green. 

Weight,  seasoned. 

Hickory,  oak 

eft  to  64. 

4.2  to  4.8 

Ash  elm  cherry  maple  walnut 

48  to  56 

36  to  42 

Hard  pine,  Oregon  pine  

40  to  48 

30  to  36 

Norway  pine,  cypress,  hemlock  

32  tO  4O 

24.  to  3O 

Cedar  spruce 

24.  to  4.O 

1  8  to  30 

White  pine  poplar 

2  A  to  32 

1  8  to  24 

Art.  3.    Faults  of  Timber* 

These  may  be  divided  hi  to  four  groups: 

(1)  Defects  of  growth. 

(2)  Faults  due  to  improper  handling  or  seasoning. 

(3)  Bacterial  decay. 

(4)  Injury  caused  by  worms  and  insects. 

Prominent  among  the  first  named  are  sapwood,  shakes,  and 
knots. 

As  already  noted,  sapwood  is  the  weaker  part  of  the  tree. 
However,  the  rejection  of  pieces  solely  on  this  account  is  justified 
only  in  timber  used  for  special  purposes. 

Shakes  are  of  two  kinds,  the  heart,  Fig.  30,  and  the  cup, 


*  Year  Book,  1911,  Am.  Soc.  Test.  Mat.,  pp.  166-172. 


6  ELEMENTS  OF  STRUCTURAL  DESIGN 

Fig.  3&.  Only  the  larger  trees  are  subject  to  them.  Small 
shakes  do  no  appreciable  harm;  those  extending  through  the 
piece  are  serious  and  justify  its  rejection. 

Knots  are  a  grave  source  of  weakness  in  timber.  Whether 
in  tension,  flexure,  or  compression,  the  safe  strength  varies 
considerably  with  number  and  size  of  knots.  A  rough  measure 
of  their  effect  in  weakening  a  piece  is  to  consider  them  as  open 
holes  of  equal  size.  In  many  cases  they  are  objectionable  for 
appearance's  sake.  It  is  generally  impracticable  to  exclude 
knots  altogether;  however;  they  should  be  limited  in  amount. 

(2)  Faults  due  to  improper  seasoning  and  handling  are 
wane,  checking,  and  case  hardening. 

Where  a  portion  of  the  exterior  surface  of  the  log  appears 
on  the  sawn  piece,  as  in  Fig.  3^,  it  is  called  a  wane.  It  signifies 


FIG.  30.  FIG.  3&.  FIG.  $c.       .  FIG. 

Heart  Shake.        Cup  Shake.          Wane.         Checking. 

the  presence  of  sapwood,  lessens  the  amount  of  timber,  and  may 
interfere  with  some  uses. 

Fig.  sd  shows  checking  which  is  a  separation  of  the  wood 
fibers  on  the  end  of  a  stick,  extending  back  into  the  piece  but  a 
short  distance.  It  is  caused  by  kiln  drying  and  may  be  pre- 
vented by  first  seasoning  in  air  for  three  to  six  months. 

Case  hardening  is  seasoning  of  the  outer  layers  before  the 
interior.  The  latter,  as  the  operation  goes  on,  shrinks  and 
checks  badly.  It  may  be  prevented  by  steaming,  or,  better 
still,  by  a  preliminary  air  drying. 

(3)  There  are  three  ways  in  which  bacteria  cause  the  decay 
of  timber: 

(a)  Fungus  growth. 

(b)  Dry  rot. 

(c)  Wet  rot. 

Fungus  growth  may  attach  itself  to  the  living  tree,  forming 
a  knob  on  the  exterior,  while  filaments  from  the  same,  in  appear- 
ance much  like  roots,  eat  into  the  tree,  and  devour  sap  and  fiber. 


MATERIALS  7 

Another  form  attacks  the  sawn  timber  in  much  the  same  manner 
as  the  mould  on  a  piece  of  bread.  Moderately  warm  localities 
with  moisture,  but  not  immersion,  and  untreated  lumber  are 
fields  suitable  to  its  growth. 

Dry  rot  is  caused  by  bacteria  which  exist  where  the  gases 
of  decomposition  cannot  escape.  Affected  wood  looks  fairly 
firm,  but  readily  crumples  to  powder  when  squeezed  between  the 
fingers.  It  spreads  rapidly,  contact  not  being  necessary  for 
infection.  Moderate  warmth,  lack  of  ventilation,  and  moisture 
but  not  immersion,  favor  its  growth. 

A  different  kind  of  bacteria  causes  wet  rot  in  timber.  This 
variety  thrives  only  where  exposed  to  circulating  air.  The 
infected  portion  is  generally  wet,  dark  or  dirty  looking,  and 
falls  to  pieces  in  the  hand.  It  spreads  by  contact  only.  Moder- 
ate warmth  and  moisture  without  continuous  immersion  are 
favorable  conditions,  Wood  is  particularly  susceptible  to 
this  form  of  decay  when  exposed  to  alternations  of  wet  and  dry. 

To  prevent  decay  due  to  these  causes  just  outlined : 

(a1)  Season,  thus  in  a  measure  depriving  bacteria  of  their 
food. 

(br)  Use  preservatives.  These  are  invariably  disinfectants, 
that  is,  poison  for  the  bacteria.  See  Art.  4. 

(cr)  Keep  under  fresh  water.  In  tidal  seas,  there  is  danger 
from  marine  worms.  (See  below.) 

(df)  Avoid  conditions  favorable  to  their  growth  as  given 
above. 

Of  these,  (cf)  is  the  only  method  that  is  always  dependable. 
Removal  of  wet  rot  already  existing  and  observance  of  any 
one  of  above  rules  should  prevent  its  spreading  farther.  For 
dry  rot,  in  addition,  all  pieces  in  vicinity  should  be  scraped 
and  washed  with  acid. 

(4)  We  shall  limit  ourselves  to  the  consideration  of  marine 
worms.*  Although  there  are  insects  which  cause  damage, 
they  are  largely  limited  to  tropical  climates. 

The  principal  of  these  pests  are : 

Teredo  or  ship  worm,  about  six  inches  long,  and  one-eighth 
inch  in  diameter. 

*  Colson's  "Notes  on  Dock  and  Dock  Construction."  Eng.  News,  Vol.  XL,. 
P- 34- 


8  ELEMENTS  OF  STRUCTURAL  DESIGN 

Limnoria  Terebrans,  a  small  insect  about  one-sixth  inch 
long  resembling  a  wood  louse. 

Chelura  Terebrans,  in  appearance  like  a  sand  shrimp.  It  is 
about  one-quarter  inch  long  and  very  destructive. 

They  inhabit  salt  water,  attacking  the  timber  between  low  tide 
and  the  bottom  of  the  sea.  Here  they  bore  in  the  wood,  in  some 
cases  leaving  but  a  small  percentage  of  the  whole.  For  protection : 

(a)  Leave  the  bark  on  (partial). 

(b)  Use  only  certain  kinds  of  woods,  for  example,  palmetto, 
cypress,  pine.     (Of  doubtful  value.) 

(c)  Drive   flat-headed   nails   of  iron,  copper,  or   zinc   close 
together.     They  should  extend  from  a  foot  below  the  ground 
to  high  water. 

(d)  Cover   timber  with   tarred  paper  and  zinc  or   copper 
sheathing  from  a  foot  below  the  ground  to  high  water. 

(e)  Creosote  the  timber.     This  is  the  best  remedy  and  will 
be  taken  up  in  the  next  article. 

Art.  4.    Preservative  Processes  for  Timber 

The  lack  of  durability  in  timber  is  caused  by  (i)  rot,  either 
wet  or  dry,  (2)  marine  worms,  and  (3)  fire.  Means  for  preventing 
destruction  by  these  agencies  will  be  discussed  in  this  article. 

The  life  of  timber  if  fully  exposed  to  marine  worms,  is 
very  short,  say  a  year  or  so.  For  an  untreated  railroad  tie 
it  is  six  to  twelve  years,  according  to  species  of  timber  and 
location.  The  use  of  tie  plates  is  expected  to  increase  this. 
The  life  of  untreated  timber  if  exposed  to  the  weather  is  ten 
to  twenty  years;  if  housed,  forty  years  or  more.  Preservatives 
will  considerably  prolong  durations  given  above. 

If  timber  be  kept  under  water  it  will  last  indefinitely.  Well 
preserved  pieces  of  wood  have  been  found  in  the  wet  strata 
of  bygone  geologic  ages.* 

Timber  to  be  buried  in  the  ground  should  be  charred  or 
dipped  in  coal  tar.  In  the  latter  case,  seasoning  is  necessary; 
in  the  former  it  is  advisable. 

Creosoting,  if  well  done,  is  the  best  of  all  preservative 
processes.  The  material,  creosote,  is  obtained  from  the  dead 

*  Eng.  News,  Vol.  LIV,  p.  555- 


MATERIALS  9 

oil  of  coal  tar  by  distillation.  The  idea  of  the  treatment  is 
to  introduce  it  into  the  pores  of  the  wood.  As  long  as  it  remains 
there,  the  pests  will  not  attack  it.  The  creosote  does  not 
penetrate  deeply,  hence  care  must  be  taken  in  making  fresh 
cuts  in  timber,  as  they  may  afford  entrance  to  its  enemies.  The 
proper  way  is  to  cut  and  remove  bark  before  creosoting.  The 
creosote  should  not  have  more  than  2|  per  cent  of  water  and 
a  specific  gravity  of  not  less  than  1.04  at  100°  F. 

In  the  process,  timber  is  first  air  dried  for  several  months, 
then  placed  in  large  cylindrical  vessels,  subjected  to  steam  at 
a  pressure  of  15  to  40  Ibs.  per  square  inch;  next  to  a  negative 
pressure  of  12  Ibs.  per  square  inch;  afterwards  to  creosote  oil 
at  a  temperature  of  120°  F.  and  a  pressure  of  150  to  200  pounds 
per  square  inch.  Five  to  twenty-five  pounds  per  cubic  foot 
of  timber  should  be  absorbed,  several  hours  being  required 
for  the  saturation.  The  larger  amounts  are  for  protection 
against  marine  worms.  Creosote  seems  to  make  timber  brittle 
and  ill  adapted  to  resist  abrasive  forces.  The  cost  of  the 
treatment  is  i.o  to  1.5  cents  per  pound  of  creosote. 

Various  modifications  of  this  process  are  in  use  but  above 
is  typical. 

Burnettizing:  In  the  same  general  manner,  other  chemicals 
may  be  introduced  into  the  wood.  In  burnettizing,  about 
|  pound  chloride  of  zinc  per  cubic  foot  is  injected  at  a  cost  of 
2§  to  6  cents  per  cubic  foot.  It  bleaches  out  very  rapidly 
with  moisture  or  water,  hence  its  field  is  very  limited.  Is  likely 
to  render  timber  brittle. 

Kyanizing:  Here  the  chemical  is  bichloride  of  mercury, 
but  like  the  chloride  of  zinc,  it  rapidly  dissolves  out  under 
the  action  of  water. 

Zinc-Creosote  Process :  For  the  sake  of  economy,  the  creosote 
and  emulsion  of  chloride  of  zinc  are  simultaneously  injected. 
Results,  however,  are  not  so  favorable  as  for  creosote  alone. 

Zinc  Tannin,  or  Wellhouse  Process:  In  this  case,  chloride 
of  zinc  is  injected,  followed  by  glue  and  tannin,  these  two 
latter  substances  forming  an  artificial  leather  which  plugs  up 
the  pores  in  the  outside  so  as  to  keep  in  the  zinc  chloride. 

Other  Processes:  Many  other  process  have  been  used 
among  which  we  will  mention: 


10  ELEMENTS  OF  STRUCTURAL  DESIGN 

(a)  Creo-resinate — creosote,  resin,  formaldehyde. 

(b)  Water  creosote — emulsion  of  creosote  and  water. 

(c)  Haselman — boiling  in  sulphates  of  iron,  copper,  etc. 

"  Fire  Proof "  Wood/  Wood  impregnated  on  pressure 
with  such  salts  as  those  of  alum,  ammonia,  and  the  phosphates 
burns  with  much  more  difficulty  than  before  treatment.  It 
acts  in  two  ways:  first,  a  deposit  is  formed  in  the  cells  which 
retards  the  flame;  second,  a  gas  is  given  off  that  hinders  com- 
bustion. This  gas  is  sometimes  quite  offensive.  There  is  no 
such  thing  as  fireproof  wood.  It  is  simply  fire  retarding. 

Art.  5.    Varieties  of  Timber 

White  pine  is  an  evergreen  tree  with  a  needle-like  leaf. 
Timber  is  a  light  whitish  color,  does  not  warp  or  check,  and  is 
hence  a  good  finishing  lumber.  Is  easy  to  work  but  lacks 
strength.  First-class  white  pine  is  scarce  and  expensive. 

Hard,  or  long  leaved  Southern,  or  yellow  pine  timber  is 
heavy,  free  from  knots,  has  a  reddish-brown  tint  and  a  resinous 
odor.  Trees  from  which  it  is  cut  grow  in  the  Southern  States. 
It  is  very  durable,  very  strong,  very  stiff,  and  stands  well, 
but  is  hard  to  work.  It  is  our  best  structural  timber. 

Norway  pine  is  common  along  the  Canadian  border.  The 
timber  is  a  white  wood  with  a  reddish  tint,  and  is  soft  and 
durable.  Its  strength  and  other  characteristics  are  intermediate 
between  those  of  white  and  yellow  pine. 

Oregon  pine  or  Douglas  fir  is  a  western  timber.  It  is  much 
like  yellow  pine,  except  that  wood  is  coarser  grained.  It  is 
stiff,  strongy  and  durable,  and  except  for  difficulty  in  working, 
an  ideal  construction  timber. 

There  are  three  varieties  of  spruce;  white,  black,  and  red, 
all  much  alike.  Timber  is  alight  whitish  or  reddish  color,  soft, 
easy  to  work,  of  medium  strength,  warps  and  twists  a  good  deal. 

Hemlock  grows  in  the  northern  United  States  and  in  Canada. 
Wood  is  light,  of  reddish  gray  color,  lacking  in  strength,  moder- 
ately durable,  cross-grained,  rough,  and  splintery.  It  shrinks 
and  warps  considerably  in  seasoning. 

There  are  several  varieties  of  cedar,  all  of  which  are  light, 

*  Eng.  News,  Vol.  LIV,  p.  353- 


MATERIALS  11 

soft,  grayish  brown  or  red  woods.  Timber  is  durable,  seasons 
rapidly,  shrinks  and  checks  but  little. 

Several  different  species  of  cypress  are  found  in  the  swamps 
of  our  Southern  States.  Wood  is  light,  soft,  easily  worked, 
straight  grained  and  free  from  knots.  It  warps  and  shrinks 
little  and  is  used  in  finishing. 

There  are  six  varieties  of  ash  of  which  the  principal  are 
white  and  black.  Timber  is  heavy,  tough,  strong,  and  hard. 

Three  kinds  of  oak  occur,  white,  red,  and  live.  The  latter 
may  be  distinguished  by  its  very  crooked  limbs;  the  others, 
by  the  color  of  the  timber.  Oak  is  hard,  tough,  and  strong. 
It  is  especially  prominent  among  timbers  by  reason  of  its  high 
shearing  strength.  It  is  difficult  to  work,  shrinks  and  cracks 
badly  in  seasoning,  but  once  seasoned,  it  stands  well.  Live 
oak  is  now  very  expensive  and  is  used  only  for  special  purposes 
such  as  in  wooden  boats.  Both  white  and  red  oak  are  extensively 
employed,  but  the  former  is  more  desirable  in  every  way. 

Beech  is  a  white  to  light  brownish  timber,  coarse  textured, 
heavy,  hard,  and  strong. 

Chestnut  is  a  light,  soft,  coarse-textured  wood.  Possesses 
only  medium  strength  but  is  very  durable. 

Poplar  or  whitewood  is  a  white  or  pale  yellowish  timber, 
very  free  from  knots.  Timber  is  light,  soft,  and  weak,  shrinks 
badly  and  warps  considerably. 

Maple  makes  a  hard,  tough,  strong  timber,  white  in  color. 
It  seasons  and  stands  well. 

Art.  6.    Strength  of  Timber 

Allowable  values  are  in  pounds  per  square  inch,  for  good 
merchantable  timber  as  received  from  the  lumber  yard.  Formula 
for  flat-ended  columns: 


Sc=a-b  — 
a 


Where, 


Sc  =  allowable  compressive  unit  stress; 
a,  b  =  constants  given  below; 

/  unsupported  length  in  inches 

— :  =  greatest  value  of  fraction r^-  .  ,   . — ; — —     — . 

a  least  breadth  in  inches 


12 


ELEMENTS  OF  STRUCTURAL  DESIGN 
BUILDINGS 


Ten- 

Flex- 

Compression. 

Bearing 

...  to  grain. 

Shear- 

Modulus 

Variety. 

of 

' 

' 

Elasticity. 

a 

b 

Per. 

Par. 

Chestnut         .... 

600 

750 

600 

6 

3OO 

IOOO 

60 

I  2OO,OOO 

White  oak 

IOOO 

IOOO 

IOOO 

12 

c;oo 

I  <OO 

iqo 

I  600  OOO 

Red  oak  

900 

900 

900 

II 

400 

I2OO 

140 

1,500,000 

Hemlock  

4.00 

600 

400 

4 

200 

7^O 

60 

900,000 

Spruce 

600 

7">o 

600 

6 

300 

IOOO 

80 

I  2OO  OOO 

White  pine  

600 

750 

600 

7 

200 

750 

60 

I,IOO,OOO 

Norway  pine  

800 

900 

800 

9 

300 

900 

70 

I,3OO,OOO 

Oregon  pine  

IIOO 

IIOO 

IIOO 

14 

300 

1400 

100 

1,500,000 

Yellow  pine  

I2OO 

1500 

I2OO 

15 

600 

1500 

IOO 

I,6OO,OOO 

TRESTLES  AND   BRIDGES 


Variety. 

Ten- 
sion. 

Flex- 
ure, j 

Compression. 

Bearing 

.  .      to  grain. 

Shear- 
ing. 

Modulus 
of 
Elasticity. 

a 

b 

Per. 

Par. 

Chestnut 

400 
750 
600 
250 
400 
4OO 
500 
700 
800 

500 
750 
600 
400 
500 
500 
600 
900 
IOOO 

400 
750 
600 
250 
400 
400 
500 
700 
800 

4 
8 

7 
3 
4 
5 
6 

9 

10 

20O 
400 
35° 
150 
2OO 

150 
2OO 
200 
4OO 

750 
IOOO 

800 
500 

750 
500 

600 

900 

IOOO 

40 
IOO 

90 
40 
50 
40 
50 
70 
70 

I,2OO,OOO 
I,6oo,OOO 
1,500,000 
900,000 
1,200,000 
1,100,000 

1,300,000 
1,500,000 
1,600,000 

White  oak. 

Red  oak 

Hemlock  

Spruce 

White  pine  

Norway  pine  
Oregon  pine  

Yellow  pine 

Above  values  may  vary  considerably.  Notice  the  marked 
weakness  of  timber  in  shear  and  bearing  perpendicular  to  the 
grain. 

The  lower  part  of  the  tree  is  stronger  than  the  upper.  In 
a  transverse  section,  the  heart  is  stronger  except  in  an  old  tree 
where  it  has  begun  to  lose  its  vitality. 

Tests  have  shown  that  boxing  a  tree  for  turpentine  does 
not  affect  its  strength.  Time  of  felling  makes  no  difference 
except  as  it  may  influence  seasoning.  Calling  the  strength  of 
timber  with  10  per  cent  moisture  100,  we  may  say  very  roughly: 


MATERIALS  -      13 

with  50  per  cent  moisture,  its  strength  is  50;  40  per  cent  moisture, 
555  30  per  cent,  65;  20  per  cent,  80.  Whether  water  is  original 
or  absorbed  seems  to  make  no  difference .  Resisting  power 
does  not  seem  to  vary  with  the  size  except  as  the  latter  affects 
seasoning.  Let  us  call  the  ultimate  load  for  the  usual  accelerated 
test  for  a  wooden  piece  100:  if  the  test  lasts  one  day,  the  load 
becomes  75;  one  week,  65;  one  year,  60. 

Art.  7.    Uses  of  Timber 

In  all  locations,  durability  and  economy  must  be  considered. 
In  various  situations,  we  have  the  following  special  requirements: 

For  posts,  girders,  joists,  trusses,  .and  roof  timbers: 

If  stresses  are  light,  ease  of  framing  is  the  principal  requisite; 
hence  use  spruce  and  hemlock. 

For  heavier  stresses,  strength  is  desirable  and  yellow  pine, 
oak,  or  perhaps  spruce  or  Norway  pine  may  be  employed. 

For  large  timbers,  either  Oregon  pine  or  yellow  pine  can  be 
obtained  in  lengths  up  to  sixty  feet. 

For  under  flooring,  a  cheap  timber  such  as  spruce  or  hemlock 
will  do.  A  wood  that  will  stand  and  wear  well  is  demanded 
for  the  upper  floors  and  thresholds;  such  are  quarter  sawn 
white  oak,  maple,  and  yellow  pine. 

For  shingles  use  cedar,  cypress,  or  white  pine;  for  siding 
and  clapboards,  the  last  two  may  be  employed;  for  doors, 
sash,  blinds,  inside  and  outside  finish,  use  white  pine  or  cypress. 

Piles  and  cribbage  may  be  designed  of  oak,  elm,  hard  pine, 
cypress,  spruce,  and  hemlock.  For  bridge  ties,  use  hard  pine 
and  white  oak. 

Art.  8.    Cast  Iron* 

Iron  ores  are  dug  from  the  earth,  and  placed  in  a  blast 
furnace  with  coke  or  some  other  fuel  and  a  flux  like  limestone 
to  carry  away  the  impurities.  The  resulting  product  is  pig 
iron.  This  is  heated  in  a  cupola  which  is  something  like  a  small 
blast  furnace.  The  melting  is  also  similar  except  that  charges 

*  Reference  for  irons  and  steels:  Johnson's  "Materials  of  Construction"; 
Campbell's  "Manufacture  and  Properties  of  Iron  and  Steel";  Stoughton's 
"Metallurgy  of  Iron  and  Steel." 


14      *  ELEMENTS  OF  STRUCTURAL  DESIGN 

of  coke  and  limestone  are  much  smaller.  The  slag  and  the 
iron  are  tapped  off,  the  latter  into  ladles  which  are  poured  as 
explained  in  Art.  16.  After  cooling,  the  box  is  taken  apart, 
the  projections  on  the  casting  cut  off,  and  it  is  then  placed  in  a 
tumbler  to  remove  the  sand.  This  is  commercial  cast  iron. 
Let  us  examine  it  with  especial  reference  to  those  imperfections 
which  so  limit  it  in  structural  work. 

Cast  iron  consists  of  about  93  per  cent  of  iron  together  with 
at  least  1.5  per  cent  of  carbon.  The  remaining  portion  is  largely 
silicon,  phosphorus,  and  manganese. 

Carbon  may  occur  in  two  forms,  the  combined  and  the 
graphitic.  The  former  is  the  important  element  in  cast  iron, 
the  effect  of  the  other  elements  being,  in  general,  to  increase 
or  decrease  it  and  in  that  way  influence  the  properties  of  the 
metal.  A  small  amount  makes  a  gray  soft  iron,  easily  worked 
and  comparatively  strong  in  tension.  On  the  other  hand,  a 
large  amount  makes  a  hard  brittle  iron. 

The  effects  of  silicon  and  aluminum  are  similar,  each  tend- 
ing to  eliminate  blowholes.  A  small  amount  of  silicon  diminishes 
combined  carbon  and  hence  softens  the  cast  iron.  A  larger 
dose  seems  however  to  make  it  brittle. 

Sulphur  also  makes  iron  hard  and  brittle  and  should  not  be 
allowed  above  .10  per  cent.  Phosphorus  up  to  .70  per  cent 
does  not  injure  the  metal,  but  helps  it  to  fill  the  mould. 

Manganese  when  alone  seems  to  harden  cast  iron,  but  with 
much  silicon  present  may  soften  it.  Tends  to  counteract  sulphur 
and  silicon. 

The  strength  of  cast  iron  in  tension  varies  from  10,000  to 
40,000,  with  an  average  of  20,000  Ibs.  per  square  inch.  In 
compression,  tests  on  small,  short  pieces  show  an  ultimate 
strength  of  50,000  to  200,000.  On  full-sized  columns,  how- 
ever, this  falls  to  20,000  to  40,000  Ibs.  per  square  inch.  The 
reasons  for  this  extraordinary  drop  will  be  discussed  presently. 
The  flexural  strength  will  vary  from  10,000  to  60,000  Ibs.  per 
square  inch.  An  average  value  of  the  modulus  of  elasticity  is 
15,000,000  Ibs.  per  square  inch. 

It  is  hard  and  resists  fire  and  corrosion  better  than  either 
wrought  iron  or  steel.  It  cannot  be  hammered,  bent,  rolled, 
or  forged.  It  is  very  likely  to  be  brittle  and  it  possesses  little 


MATERIALS  15 

elasticity  or  resistance  to  shock.  It  is  liable  to  blowholes,  to 
segregation,*  and  to  stresses  due  to  the  shrinkage  of  the  interior 
after  the  exterior  has  cooled.  The  last  named  are  often  termed 
"  shrinkage  "  or  "  initial  "  stresses.  Displacement  of  core  in 
castings  may  occur  and  leads  to  the  extremely  objectionable 
eccentric  sections. 

As  might  be  expected,  such  a  material  has  proven  unsatis- 
factory for  engineering  purposes.  It  is  employed  largely  in 
locations  where  the  stresses  are  small,  compressive,  and  quiescent 
or  nearly  so;  for  example,  in  bearing  blocks  and  washers. 
Cast  steel  is  now  displacing  cast  iron  in  many  places. 

Castings  should  be  of  tough  gray  iron  with  not  over  o.io 
per  cent  of  sulphur.  They  must  not  contain  any  blowholes 
or  other  flaws.  Test  pieces  i  in.  square  must  show  a  modulus 
of  rupture  not  less  than  40,000  Ibs.  per  square  inch. 

Art.  9.    Wrought  Iron 

Wrought  iron  may  be  denned  as  iron  almost  chemically 
pure,  intermixed  with  more  or  less  slag.  A  typical  wrought 
iron  will  contain  about  0.06  per  cent  carbon,  0.09  per  cent 
silicon,  0.15  per  cent  manganese,  0.009  per  cent  sulphur,  and 
o.i  2  per  cent  phosphorus. 

Pig  iron  from  the  blast  furnace  and  iron  ore  are  heated 
together  in  a  puddling  furnace.  The  resulting  metal  is  squeezed 
and  rolled  out,  giving  it  that  fibrous  quality  which  is  char- 
acteristic of  wrought  iron. 

The  influence  of  carbon  and  silicon  is  to  make  the  iron 
hard  and  brittle.  There  should  not  be  over  0.25  per  cent 
phosphorus,  as  it  causes  "  cold  shortness,"  that  is,  brittleness 
while  cold.  Sulphur  should  be  limited  to  0.05  per  cent,  as  it 
is  likely  to  cause  "  red  shortness,"  or  brittleness  when  hot. 

The  strength  of  wrought  iron  in  tension  along  the  grain 
varies  from  45,000  to  55,000  Ibs.  per  square  inch,  elastic  limit 
from  23,000  to  40,000.  Tensile  strength  crosswise  of  the  grain 
will  average  80  per  cent  of  the  above.  Percentage  of  elongation, 
5  to  30;  reduction  of  area,  10  to  40  per  cent.  Shearing  strength 
is,  in  either  direction,  80  per  cent  of  tensile. 

*  The  concentration  of  certain  elements  in  a  part  of  the  casting. 


16  ELEMENTS  OF  STRUCTURAL  DESIGN 

Due  to  the  ductile  nature  of  the  material,  short  specimens 
do  not  fail  in  compression  but  grow  stronger  with  increasing 
loads.  Elastic  limit  is  about  the  same  in  tension  and  compres- 
sion. Longer  specimens  fail  by  buckling.  Tetmajer  gives : 

Sc=  43,000  —  1845,  s  =  iotoii2, 

=  282,000,OOO/S2  >II2, 

where  s  is  the  slenderness  ratio.* 

Certain  shapes,  like  rounds  or  squares,  will  not  break  in 
flexure  owing  to  the  ductility  of  the  specimen.  For  some  rolled 
sections  or  built  beams,  there  is  a  chance  for  failure.  If  properly 
designed,  they  will  show  a  modulus  of  rupture  of  40,000  to 
50,000  Ibs.  per  square  inch  and  a  coefficient  of  elasticity  of 
*'  25,000,000. 

Wrought  iron  is  a  ductile  metal;  it  can  be  welded,  rolled, 
or  forged;  it  will  stand  a  great  deal  of  abuse  without  injury. 
It  probably  resists  corrosion  better  than  steel.  From  above 
properties,  it  may  be  seen  that  it  is  an  excellent  structural 
material;  however,  the  greater  strength  of  steel  has  given  it  a 
preference  over  wrought  iron.  Its  use  since  1900  has  been  con- 
fined largely  to  blacksmith's  work. 

The  following  specifications  for  merchant  iron,  Grade  "A," 
were  proposed  by  Association  for  Testing  Materials. 

Tensile  strength,  50,000  Ibs.  per  square  inch  or  more. 
Yield  point,  25,000  Ibs.  per  square  inch  or  more. 
Elongation  in  8  ins.,  25  per  cent  or  more. 

Must  show  a  long  clean  silky  fiber  when  nicked  and  broken. 
A  piece  shall  bend  cold  180  degrees  flat  on  itself  without  fracture. 
Must  be  straight,  smooth,  free  from  cinder  spots  or  flaws, 
buckles,  blisters,  or  cracks. 

Art.  10.    Bessemer  Steel 

Melted  pig  iron  is  introduced  into  the  converter  and  a 
blast  of  air  is  passed  through  it.  After  this  has  oxidized  out 
the  impurities,  spiegeleisen,  an  iron  rich  in  carbon  and  manganese, 

unsupported  length 

*  Maximum  value  of  fraction  — — . 

least  radius  of  gyration 


MATERIALS  17 

is  added.  The  latter  element  unites  with  the  oxygen,  while 
the  former  gives  to  the  steel  the  proper  carbon  content. 

There  are  two  methods  of  manufacture:  the  acid  and  the 
basic;  in  the  latter,  calcined  lime  is  added  to  the  molten  steel 
to  eliminate  the  phosphorus.  While  there  is  a  slight  preference 
for  the  basic  on  account  of  the  lessened  danger  of  an  excess  of 
phosphorus,  engineers  usually  fail  to  specify  either  kind,  but 
state  permissible  limit  of  this  objectionable  element. 

The  product  may  be  divided  into  soft  steel,  containing 
0.15  per  cent  carbon;  medium,  0.30  per  cent;  hard,  0.50  per  cent. 
The  lower  carbon  content  give  us  a  ductile  metal,  possessing 
almost  unlimited  capacity  for  abuse.  It  is,  however,  weak 
compared  with  the  hard  steels  which,  on  the  other  hand,  are 
quite  brittle.  For  structural  work,  we  use  either  soft  or  medium, 
preferably  the  former  if  there  is  much  forging.  Where  high 
stresses  are  to  be  resisted,  medium  steel  is  better.  This  paragraph 
applies  also  to  open  hearth  steel  as  considered  in  next  article. 

Silicon  increases  strength  and  hardness  and  decreases  ductility. 
Manganese  in  small  quantities  makes  metal  hard  and  malleable. 
Sulphur  and  phosphorus  are  both  objectionable  elements, 
making  metal  hot  and  cold  short  respectively.  Both  should 
be  limited  to  very  small  amounts. 

For  reasons  which  will  be  given  in  the  next  article,  the 
Bessemer  process  is  used  for  structural  steel  only  in  inferior 
work.  A  great  dea.1  of  the  rail  tonnage  is  Bessemer  steel,  but 
even  here,  it  is  being  displaced  by  the  open  hearth  process. 

Strength  and  tests  will  be  discussed  under  the  head  of 
open  hearth  steel,  which  it  closely  resembles.  For  rails,  it 
is  usual  to  specify  the  drop  test  and  a  chemical  composition 
about  as  follows:  carbon,  0.45  per  cent;  manganese,  0.90  per 
cent;  silicon,  not  to  exceed  0.20  per  cent;  phosphorus,  not  to 
exceed  o.io  per  cent. 

Art.  ii.    Open  Hearth  Steel 

«  In  this  process,  pig  iron,  scrap,  and  iron  ore  are  subjected 
to  an  oxidizing  flame  in  an  open  hearth  furnace.  When  carbon 
has  been  lowered  to  the  proper  amount,  spiegeleisen  or  ferro- 
manganese  is  added  which  combines  with  the  oxide  of  iron  and 


18 


ELEMENTS  OF  STKUCTURAL  DESIGN 


prevents  further  loss  of  carbon.  As  in  Bessemer  steel,  we  have 
the  acid  and  the  open  hearth  processes,  also  soft,  medium,  and 
hard  steels.  The  effect  of  the  elements  is  substantially  the 
same  in  both  cases. 

Bessemer  is  the  cheaper  method  but  gives  poorer  material. 
Open  hearth  is  more  uniform  and  more  reliable.  The  process  is 
such  that  it  can  be  better  regulated  to  produce  required  com- 
position of  metal.  Always  specify  open  hearth  for  important 
structural  work.  We  may  use  medium,  soft,  or  rivet  steel,  the 
latter  being  very  soft  and  ductile. 

American  Association  for  Testing  Materials  recommend 
following  specifications : 

No  grade  should  have  more  than  0.08  per  cent  phosphorus, 
not  more  than  0.06  per  cent  sulphur.  The  finished  material 
should  be  free  from  injurious  seams,  flaws,  or  cracks.  In 
addition  the  following  requirements  should  be  fulfilled: 


Rivet  Steel. 

Soft  Steel. 

Medium  Steel. 

Tensile  strength,  Ibs.  per  sq.in.  . 
Yield  point,  Ibs.  per  sq.in.  (not 
less  than) 

50,000  to  60,000 
one- 

26 
180° 
flat  on  itself. 

52,000  to  62,000 
half  tensile  stre 

25 
180° 
flat  on  itself. 

6o,OOO  to  70,000 
ngth 

22% 

180° 
around  its 
own  thickness. 

Elongation  in  eight  inches  (not 
less  than)  

Cold  j                                       ( 

Bend) 

The  strength  of  steel  will  vary  according  to  its  impurities. 
Carbon  is  the  most  important  element  in  its  influence  on  strength. 
This  in  tension  for  a  small  specimen  may  be  gauged  by  the  phys- 
ical requirements  just  given.  Shear  will  average  80  per  cent 
of  the  tensile  stresses.  Compression  for  small  specimens  has 
about  the  same  elastic  limit  as  in  tension.  For  full-size  pieces, 
we  find  a  large  reduction  in  breaking  loads,  particularly  in  com- 
pression. While  data  for  definite  conclusions  are  lacking,  it 
looks  as  though  the  ultimate  stress  in  a  full-size  column  might, 
even  with  what  are  now  considered  sound  details,  fall  as  much 
as  50  per  cent  below  that  for  a  small-sized  specimen.  (Art.  69.) 


MATERIALS  19 

The  coefficient  of  elasticity  is  in  the  vicinity  of  30,000,000  Ibs. 
per  square  inch. 

Many  shop  processes  such  as  punching,  shearing,  and 
bending  the  metal,  either  hot  or  cold,  cause  stresses  while  still 
without  load.  These  are  called  "  initial  stresses."  Another 
cause  is  the  rapid  cooling  of  metal  after  heating  for  forging.  To 
remove  this  undesirable  condition,  metal  is  heated  to  about 
1200°  F.,  and  allowed  to  cool  very  slowly  and  uniformly.  This 
process  is  called  annealing. 

Cast  iron  costs  about  2.5  cents  per  pound  when  patterns 
are  furnished;  cast  steel  under  the  same  circumstances,  4  cents. 
Steel  or  wrought  iron  will  cost  1.2  cents  as  rolled  or  about  2.5 
cents  as  fabricated,  f.o.b.  cars  at  shop. 

Art.  12.    Cast  Steel  and  Alloys  of  Steel 

The  process  of  casting  as  outlined  briefly  in  Art.  16,  gives 
notable  economy  in  the  fabrication  of  shapes  possessing  an 
intricate  form.  But,  as  already  pointed  out,  cast  iron  has 
faults  which  limit  its  application  in  structural  work.  Of  late, 
the  practice  of  making  the  castings  of  open  hearth  steel  has  grown 
steadily  in  favor.  As  in  structural  shapes,  the  material  may  be 
soft,  medium,  or  hard  steel.  The  latter,  like  rolled  stuff,  is 
unsuitable  for  structural  purposes.  The  properties  of  the  result- 
ing castings  are  much  the  same  as  those  of  the  metal  from 
which  it  is  poured.  Thus,  if  soft  steel  be  used,  it  will  be  ductile, 
show  a  large  resistance  to  impact  tests,  have  a  high  elastic  limit 
and  a  definite  yield  point.  Blowholes,  cracks,  and  segregation 
are  the  faults  to  be  guarded  against.  Complicated  castings 
should  be  annealed. 

We  shall  speak  of  but  two  alloys  of  steel,  vanadium  and 
nickel.*  Both  seem  to  increase  strength  to  a  remarkable  degree 
without  interfering  with  its  toughness.  In  fact  it  is  claimed 
that  vanadium  increases  it. 

Nickel  steel  has  actually  been  used  in  bridge  work,  and  it 
is  doubtless  the  material  of  the  future  for  long-span  structures. 
The  usual  percentage  is  three  to  three  and  one-half  and  the 
steel  to  which  it  is  added  commonly  open  hearth.  More  car- 

*  See  Waddell's  paper,  "  Nickel  Steel  for  Bridges,"  Trans.  A.S.C.E.,  Vol.  LXIII. 


20  ELEMENTS  OF  STRUCTURAL  DESIGN 

bon  may  be  used  than  would  be  allowable  without  the  nickel. 
Such  an  alloy  will  have  an  elastic  limit  about  equal  to  the  tensile 
strength  of  the  steel  and  an  ultimate  strength  80  per  cent 
greater.  In  compression,  the  excess  will  vary  from  50  to  75 
per  cent,  the  latter  for  short  struts.  The  coefficient  of  elasticity 
is  unchanged.  Nickel  steel  does  not  stand  shop  abuse  as  well 
as  carbon  steel,  but  it  is  nevertheless  satisfactory.  Shopwork 
such  as  punching,  drilling,  and  chipping,  will  be  more  expensive. 
Nickel  steel  seems  in  general  to  resist  corrosion  better. 

Art.  13.    Paints  * 

Very  little  is  known  in  regard  to  the  theory  of  the  preserva- 
tion of  wood  by  the  use  of  paint.  For  steel,  however,  con- 
siderable has  been  done  in  this  respect.  It  is  now  considered 
that  rust,  the  principal  enemy  of  steel,  is  due  to  the  electrolytic 
action  between  the  hydrogen  of  the  water  and  the  iron.  Oxygen 
must  be  present.  Also,  some  acids,  for  instance  the  carbonic 
acid  always  in  the  air,  accelerate  the  rusting.  To  prevent  this 
action,  we  have  "  inhibitors "  or  rust  preventers.  Alkalies 
act  as  such,  also  chromic  acid  and  its  salts.  The  former 
cannot  be  used  with  ordinary  paints  made  of  linseed  oil,  because 
they  unite  with  the  latter  to  form  soap.  This  objection  does 
not  hold  for  the  chromates,  and  they  make  excellent  inhibitive 
paints. 

Carbonic  acid,  oxygen,  and  moisture  are  always  present  in 
the  air,  and  hence  unprotected  steel  will  rust.     One  excellent 
preventive  method,  encasing  in  concrete,  will  be  taken  up  in 
Vol.  II.     We  will  now  consider  the  other  method,  protection, 
by  paint. 

This  usually  consists  of  an  aggregate  of  pigment  with  a 
cementing  material  of  linseed  oil.  Pure  linseed  oil  is  made  by 
crushing  flaxseed,  and  allowing  it  to  stand  and  settle  and  thus 
purify.  In  this  form,  it  is  known  as  raw  linseed  oil,  which  dries 
or  oxidizes  very  slowly.  This  process  may  be  hastened  by 
adulterating  with  japan  drier  or  by  boiling.  Former  makes 
oil  poorer  as  a  paint,  while  latter  process  is  expensive. 

*  Cushman  and  Gardner's  "  Corrosion  and  Preservation  of  Iron  and  Steel.'* 
Ketchum's  "Steel  Mill  Buildings,"  Chap.  XXVII. 


MATERIALS  21 

Pigment  should  be  finely  ground,  preferably  in  oil.  For 
it,  the  following  substances  may  be  used: 

White  lead  (hydrated  carbonate  of  lead),  is  employed  for 
wood  and  for  finished  surfaces  in  steel.  Disintegrates  when 
attacked  by  corrosive  gases  and  does  not  make  a  good  bottom 
coat. 

Red  lead  (lead  tetroxide),  is  very  stable,  either. on  exposure 
to  light  or  the  weather.  Is  probably  the  best  paint  for  metal. 
It  is  mildly  inhibitive,  but  is  improved  by  the  addition  of  3  per 
cent  of  zinc  chromate. 

Zinc  oxide  has  a  tendency  to  peel  but  when  mixed  with 
red  lead  makes  a  good  paint  for  metal  surfaces. 

Iron  oxide  is  sometimes  used.  It  should  be  free  from  the 
hydrated  oxide. 

Carbon,  when  mixed  with  linseed  oil,  has  a  large  covering 
capacity  with  a  correspondingly  reduced  protection. 

Structural  work  will  average  150  to  250  sq.ft.  per  ton  of 
metal.  Common  practice  is  to  estimate  \  gallon  per  ton  per 
coat. 


CHAPTER  II 

COMMERCIAL  SHAPES 

Art.  14.    Handbooks,  Units,  and  Dimensions 

THE  leading  manufacturers  publish  books  which  give  the 
details  and  properties  of  the  different  shapes  rolled  by  them, 
and  a  great  deal  of  other  data  which  are  very  useful  to  the  drafts- 
man and  designer.  Prominent  among  these  are  the  handbooks 
prepared  by  the  Cambria  Steel  Co.,  the  Bethlehem  Steel  Co., 
and  the  Carnegie  Steel  Co.  This  additional  information  usually 
consists  of  safe  loads  for  different  shapes,  either  as  a  beam 
or  as  a  column;  radii  of  gyration  and  capacity  of  common 
types  of  built-up  columns;  values  for  rivets  and  pins;  details 
of  bolts,  rivets,  nuts,  upset  ends,  eyebars,  turnbuckles,  sleeve- 
nuts,  clevis  nuts,  pins,  loop  rods,  and  nails;  weights  and  areas 
of  plates  and  round  or  square  bars. 

A  problem  of  frequent  occurrence  is  to  find  the  hypothenuse 
of  a  right-angled  triangle  when  both  legs  are  given  in  feet, 
inches,  and  fractions  of  an  inch.  This  is  a  very  cumbersome 
operation  without  the  aid  of  tables  of  squares.  Hall's  Tables 
($2.00)  may  be  recommended,  while  Smoley's  ($3.00)  are  still 
better.  The  latter  also  contains  logarithms  of  numbers  and 
sines,  tangents,  and  secants,  which  may  be  used  to  advantage 
in  figuring  triangles.  For  large  distances  and  for  bridges  built 
on  a  curve,  a  seven-place  logarithmic  table  of  numbers  and 
trigonometrical  functions  is  advisable. 

A  number  of  very  good  books  have  been  written  with  the 
idea  of  still  further  assisting  the  draftsman.  Such  are  Godfrey's 
"Tables,"  Osborn's  "  Moments  of  Inertia,"  and  Sample's 
"  Properties  of  Steel  Sections." 

In  continental  Europe,  the  metric  system  is  employed  in 
structural  work.  It  would  be  convenient  here,  but  the  expense 
attendant  upon  such  a  change  of  units  has  hitherto  prevented 
its  adoption. 

22 


COMMERCIAL  SHAPES  23 

Dimensions  of  wires  and  thin  plates  are  commonly  given 
in  gage  numbers.  For  sheet  steel,  the  United  States  Standard 
Gage  is  used  and  a  sheet  may  be  specified  thus — i  PI.,  i6"X 
No.  20  U.  S.  Standard  gageX3/~4//.  Unfortunately,  there 
are  several  different  "  standards,"  no  two  of  which  are  alike. 
This  makes  it  necessary  to  name  the  one  employed,  as  above, 
unless  it  is  definitely  understood  by  all  concerned.  A  new 
gage,  the  "  standard  "  decimal  gage,  has  been  recently  adopted 
by  the  Association  of  American  Steel  Manufacturers,  in  which 
the  gage  is  expressed  in  even  decimals  of  inches.  Its  universal 
adoption  would  obviate  the  confusion  now  arising  from  the 
multiplicity  of  systems.  Tables  giving  the  equivalents  of 
the  different  gages  may  be  found  in  structural  handbooks. 

Except  as  above  noted,  the  units  of  measurements  are  the 
foot,  inch,  and  the  thirty-second  of  an  inch.  Save  the  dimensions 
of  pin-holes  which  will  be  taken  up  later,  the  following  rules 
must  be  observed : 

(1)  All  distances  are  to  be  computed  to  the  nearest  thirty- 
second  of  an  inch. 

(2)  All  distances  except  dimensions  of  castings,  shapes,  and 
plates,  when  12"      or  over  must    be    expressed   in  feet  and 
inches— thus,  i'-6i",  not  i81". 

(3)  The  fractions  of  an  inch  must  be  reduced  to  its  lowest 
terms,  thus,  i'-6i",  not  i'-6&". 

(4)  Machinists  and  pattern  makers  prefer  dimensions  up 
to  two   feet  in  inches.     In  structural  drawings 

involving  these  classes  of  work,  this  rule  may  or 
may  not  be  followed. 

(5)  The  method  of  giving  the  dimensions  of 

plates  and  shapes  stated  in  the  following  articles  FIG      _Method 

must  be  Used.  of      Specifying 

The  only  angle  which  the  workman  is  sup-       Angles, 
posed  to  understand  is  90  degrees;    all  others 
must  be  given  in  bevels,  that  is,  by  drawing   a   right   triangle 
with  one  side   of  the  angle  as   the  hypothenuse  and   the  two 
legs  drawn  parallel  and  perpendicular  to  the  other  side.     For 
example,  an  angle  of  56  degrees  and   30  minutes  is  expressed 
as  shown  in  Fig.  14,  the  longer  leg  always  being  12". 


24 


ELEMENTS   OF  STRUCTURAL  DESIGN 


Art.  15.    Commercial  Shapes  of  Wood 


Fig.  i$a  shows  the  ordinary  way  of  cutting  up  logs; 
the  timber  is  then  known  as  "  bastard  sawed."  Fig.  156 
shows  the  method  taken  to  produce  "  quarter  "or  "  rift " 
sawed  lumber.  The  middle  boards  in  Fig.  150  are  sometimes 
sold  for  quarter  sawed  stuff.  Bastard  sawed  is  cheaper  but 
does  not  stand  well,  on  account  of  the  tangential  shrinkage. 

With  few  exceptions,  timber  is  sawTt  into  rectangular  shapes. 
Rough  boards  are  commonly  i",  ij",  ij",  2" ',  or  2\"  thick. 
In  the  following  table,  a  *  indicates  that  the  given  size  may 
usually  be  obtained,  although  the  list  will  vary  somewhat  with 
the  locality.  Larger  sizes  may  be  had,  but  they  are  to  be  used 
with  caution  since  they  are  more  expensive  per  foot,  B.M., 
more  likely  to  season  improperly,  to  contain  sap-wood,  decayed 


FIG.  150. — Bastard  Sawed.          FIG.  156. — Quarter  Sawed. 

heartwood,  or  other  faults.  Sizes  in  the  lower  left-hand  corner 
are  not  common,  since  their  use  is  inadvisable.  Besides  the 
reasons  just  given,  a  beam  whose  thickness  is  less  than  one- 
seventh  the  depth  has  a  tendency  to  buckle.  While  good  size 
timbers  may  be  obtained  up  to  a  length  of  60  feet,  cost  per 
foot  for  any  given  size  increases  rapidly  above  20  feet.  Stock 
lengths  are  usually  10,  12,  14,  and  16  feet. 

THICKNESS 


Depth. 

2" 

3" 

4" 

6" 

8" 

10" 

12" 

14" 

1  6" 

2' 

3' 

4' 

6' 

8' 

10' 

* 

. 

# 

* 

12 

14' 



* 

* 

* 

16' 

* 

* 

* 

* 

COMMERCIAL  SHAPES  25 

When  it  is  desired  to  give  the  wood  a  smooth  finish,  it  is 
planed,  A"  to  i"  (varying  with  size)  being  taken  off  for  each 
planing.  Hence  in  specifying  planed  stuff,  we  should  make 
it  such  dimensions  that  it  could  be  readily  cut  from  stock 
material;  thus  we  specify  flooring  as  £",  if",  if",  if",  and  so 
forth,  to  be  made  from  i",  i}",  ij",  and  2"  plank. 

Figs.  15^,  d,  and  e  give  forms  for  tongued  and  grooved 
timber.  The  purpose  of  the  groove  in  the  bottom  of  i$d  is 
to  lessen  the  effect  of  warping. 

Shingles  are  wedged-shaped  pieces  of  wood,  &"  to  \"  thick 


FIG.  isc.        FIG.  i$d.  FIG.  156.  FIG.  is/.  FIG.  15^. 

Tongued  and  Grooved  Timber.  Clapboard.  Mouldings. 

at  the  butt,  14  to  1 6"  long,  and  3  to  14"  in  width.     A  clapboard 
may  be  defined  as  a  shingle  6"  long  and  4'  wide. 

A  piece  of  wood,  small  in  section  and  used  for  trimming 
is  called  a  moulding,  Fig.  15^.  There  is  almost  infinite  variety 
to  their  shape,  and  they  may  often  be  obtained  ready  made 
from  the  lumber  dealer,  or  ordered  from  the  planing  mill. 

Art.  1 6.     Commercial  Shapes  for  Cast  Iron  and  Steel  Castings 

Molten  iron  or  steel  is  poured  in  a  space  formed  by  burying 
in  sand  a  piece  of  wood  called  the  pattern  and  then  withdrawing 
it.  This  pattern  is  a  duplicate  of  the  desired  rough  piece 
except  that  it  is  a  trifle  larger  to  allow  for  the  shrinkage  of  the 
hot  metal.  In  order  to  make  this  space,  the  box  which  contains 
the  sand  should  be  cut  by  one  or,  for  intricate  castings,  two 
or  more  "  parting  lines  "  or  lines  at  which  the  box  separates 
to  remove  the  pattern.  Holes  are  usually  formed  by  "  cores  " 
which  are  prisms  of  a  section  same  as  the  desired  shape  of  the 
hole.  These  extend  into  recesses  left  by  the  pattern  in  the 
sand. 

The  principles  which  are  of  importance  follow: 
(i)  The  parting  line  must  be  so  chosen  that  the  pattern 
may  be  withdrawn.     This  is  important  since  economy  demands 
as  few  parting  lines  as  possible. 


26  ELEMENTS   OF  STRUCTURAL  DESIGN 

(2)  Surfaces  which  are  shown  on  •  the  drawing  as  parallel 
to  the  line  of  withdrawal  of  the  pattern  are  tapered  by  the 
pattern  maker  about  A"  per  foot  to  prevent  disturbance  of 
the  sand  when  the  pattern  is  taken  out. 

(3)  The  thickness  of  the  metal  of  the  casting  should  be 

between  \"  and  if" ',  preferably  between 
J  and  i".  If  smaller  than  \n ',  it  should 
not  be  used  in  important  positions;  if 
larger  than  r|",  make  holes  enough  in  it 
to  cut  down  metal,  taking  care  to  con- 
serve the  necessary  strength.  Thus  if  it 
were  required  to  make  a  casting  2/-o//X 
FIG.  i6.-Typical  Casting,  i'-/'  and  4"  high,  it  should  not  be^made 
solid  but  somewhat  as  shown  in  Fig.  16, 

the  number  of  ribs  being  dependent  on  the  strength  required. 
This  is  done  to  avoid  the  initial  stresses  caused  by  the  unequal 
cooling  of  different  thicknesses.  These  alone  are  sometimes 
sufficient  to  break  a  casting.  As  noted  in  Art.  14,  i'-4"  is  often 
expressed  as  16"  for  convenience  of  pattern  maker. 

(4)  Surfaces  of  revolution   arid  plane   surfaces   are   easiest 
to  make   and   to  handle,   hence   they   should  be  used  where 
possible. 

(5)  Two   plane   surfaces   are   not   allowed   to   come   to   an 
intersection,  but  are  joined  by  a  curved  surface  of  perhaps 
\"  radius,  as  the  casting  tends  to  crack  at  a  sharp  angle.     The 
draftsman  gives  dimensions  to  the  meeting  point,  but  should 
show  the  rounding  of  the  edges,   without    giving  the  radius, 
as  the  pattern  maker  takes  care  of  this. 

(6)  Surfaces    which    must    be    exact   and  for    which  small 
variations    of    A    to    f"    would    not    be     permissible,    should 
be  marked  "  finish  "  or  some  abbreviation  therefor.     Designer 
should  give  dimensions  of  finished  piece  and  the  pattern  maker 
will  add   the   necessary  amount.     He   also   takes   care   of   the 
shrinkage  by  using  a  shrink  rule  which  is  just  enough  longer 
than  the  ordinary  rule  to  allow  for  the  shrinkage  of  the  metal 
when  cooling,  usually  about  \"  in  a  foot. 

(7)  Holes  for  bolts,  pins,  and  so  forth,  may  be  marked, — 
'"  Core  for   ...  .dia.  bolts,"  in  case  a  rough  fit  is  desired;    or 
"  Drill  for  ....  dia.  bolts,"  in  case  more  exact  work  is  wanted. 


COMMERCIAL  SHAPES  27 

When  designed  for  important  duties,   a  bolt  may  be  turned 
down  and  the  hole  made  .002  to  003"  larger. 

(8)  Castings   may   be   riveted   but   bolting  is   much   more 
common. 

Art.  17.    Rolling 

An  ingot  weighing  twenty  to  thirty  times  as  much  per  foot  as 
the  product  and  of  sufficient  length  to  furnish  the  desired  amount 
of  the  finished  shape,  is  passed  between  the  rolls.  These  are 
so  shaped  that  the  piece  is  reduced  to  its  proper  dimensions 
by  gradual  steps.  The  hot  metal  tends  to  squeeze  in  between 
the  rolls  leaving  projections  called  "  fins,"  Fig. 
176,  which  tendency  may  be  reduced  by  rolling 
with  the  joint  at  a  different  place. 

Auxiliary  rolls,  at  right  angles  to  the  main 
ones,  are  often  used  to  advantage.     An  example 
of  this  is  the  "  universal  mill,"  which  rolls  edges  FIG~7a._Arrange- 
of  plates  as  well  as  its  flat  sides,  Fig.  iya.  ment  of'  Rolls  in 

Rolling  iron  or  steel  is  a  big  trade  in  itself    Universal  Mill, 
which  we  cannot  enter  into  here.    We  will  only 
attempt  a  few  of  the  general  principles  as  a  means  of  under- 
standing the  common  shapes  and  as    a   guide    in    case    new 
sections    are  desired.      The    latter  should   be   avoided   except 
where  the  tonnage  will  be  sufficient  to  justify  it. 

(i)  Metal  must  not  be  too  far  from  the  axis  of  rolling;* 


FIG.  176.     FIG.  i;c.      FIG.  17 d.       FIG.  170.     FIG.  iy/.     FIG.  17 g.    FIG.  17 A. 

for  the  consequent  variation  in  the  lineal  speed  of  the  rolls 
injures  the  metal. 

(2)  Projections  at  right  angles  to  this  axis  must  have  a 
bevel.     Thus  a  tee   must   be  rolled  as  shown  in  Fig.  lye,  and 
not  as  given  in  Fig.  i  jd. 

(3)  Reentrant  angles  can  be  made  only  by  the  use  of  auxiliary 
rolls  after  the  final  or  "  finishing  "  pass.     Thus  the  shape  shown 

*  The  center  of  gravity  line  of  the  rolled  shape. 


28  ELEMENTS  OF  STRUCTURAL  DESIGN 

in  Fig.  170  must    be  rolled    as  seen  in  Fig.  iy/  and  bent  by 
the  auxiliary  rolls. 

(4)  Sections  should  be  so  designed  as  to  cool  evenly  and 
thus  avoid  curling  after  rolling  and  the  initial  stresses  due  to 
one  part  cooling  after  another.     A  square  rod  must  be  rolled 
as  shown  in  Fig.  ijg,  for,  if   first  made  square,  it  will   shrink 
to  the  form  seen  in  Fig.  ly/j. 

(5)  Plates    ordered    to    a    certain    thickness    may    overrun 
their   theoretic   weight   by   from  3    to    10   per   cent   or   even 
more.     Actual  amount  for  different  sized  plates  may  be  taken 
from  the  handbooks. 

(6)  Unless  a  special  price  is  paid,  material  is  likely  to  vary 
from  the  specified  length.     The  amount  changes  with  the  size, 
shape,  and  length,  see  Art.  58. 

The  limitations  above  given,  especially  (i),  interfere  with 
the  development  of  an  I-beam  which  possesses  maximum 
economy  as  a  beam.  The  Grey  process  of  rolling,  compara- 
tively new,  obviates  this. 

"  The  method  of  rolling  comprises  essentially  a  set  of  rolls 
with  axes  placed  parallel  to  the  web  and  working  the  inner 
profile  of  the  beam,  and  a  second  set  of  rolls  with  axes  ncrmal 
to  the  web  which  works  the  outer  faces  of  the  flanges.  The 
speeds  of  the  two  sets  of  rolls  and  their  diameters  are  so  related 
as  to  produce  homogeneity  of  structure.  A  feature  of  commercial 
importance  is  the  adjustable  support  of  the  rolls,  permitting, 
for  instance,  a  variation  in  weight  by  increase  of  flanges  alone, 
or  by  increase  of  flanges  and  web  in  any  specified  proportion 
and  that  without  changing  rolls." 

Claims  are  made  by  those  who  own  and  control  the  patents 
that  this  process  produces  a  superior  metal,  free  from  internal 
stresses.  This  is  disputed  and  the  counterclaim  advanced  that 
the  metal  is  not  as  strong  inch  for  inch  as  the  old  method  of 
rolling.  Tests  which  will  settle  the  question  of  superiority 
should  be  awaited. 

Rounds  are  often  cold  rolled.  In  this  process,  the  hot 
rolled  product  is  pickled  in  acid  to  remove  the  scale  and  rolled 
cold  between  chilled  cast-iron  rolls.  Shafts  made  in  this  way 
may  be  obtained  up  to  five  inches  in  diameter.  Rounds  less 

*  Eng.  News,  Vol.  XLVI,  p.  387. 


COMMERCIAL  SHAPES 


29 


than  one-quarter  inch  in  diameter  are  wire  drawn,  that  is, 
drawn  cold  through  a  groove  smaller  than  the  original  diam- 
eter. 

Steel  which  has  a  varying  section  or  that  which  is  too  large 
to  be  rolled,  must  be  cast  or  forged.  The  preceding  article 
explains  former  process;  in  the  latter  the  hot  ingot  is  hammered 
into  the  required  shape. 

In  the  manner  just  indicated,  many  different  shapes  are 
rolled.  For  the  present  we  shall  limit  ourselves  to  those  used 
in  structural  work  They  may  be  classified  as  common,  occa- 
sional, and  rare,  in  accordance  with  the  frequency  of  their 
occurrence  in  this  treatise. 


Common. 

Occasional. 

Rare. 

Circular 

T-beams 

Deck  beams 

Rectangular 
Angles 
I-beams 
Channels 

Z-bars 
Rails 
Trough  sections 
Column  sections 
Pine 

Bulb  angles 
Oblique  angles 
Splice  angles 

The  actual  sections  in  which  these  shapes  are  commonly 
rolled  may  be  obtained  from  the  handbooks.  The  maximum 
lengths  are  also  sometimes  given  there,  or  they  may  be  secured 
by  consulting  the  mills. 

We  shall  now  take  up  some  of  the  principal  facts  in  relation 
to  each  shape. 


Art.  18.    Circular  Shapes 

These,  as  their  name  implies,  are  true  cylinders.  They 
may  be  drawn,  hot  rolled,  cold  rolled,  or  forged.  Circular 
shapes  are  termed  wires  if  less  than  one-quarter  inch  in  diameter; 
if  more,  rounds  or  rods.  We  seldom  use  less  than  one-half  inch 
in  structural  work. 

By  "  one  inch  rod,"  we  mean  that  its  diameter  is  .one  inch. 
In  ordering  or  in  specifying  on  plans,  always  describe  thus:  , 


30  ELEMENTS  OF  STRUCTURAL  DESIGN 

8  Rounds,  7!"  dia.  Xi'-6J"; 
80s  7f"dia.  Xi'-6i", 


or, 


always  placing  the  length  last. 

Circular  shapes  may  be  obtained  in  all  sizes  from  a  fine 
wire  up  to  a  shaft  two  feet  in  diameter.  Above  7",  rounds  are 
forged;  from  J  to  2",  they  vary  by  sixteenths;  from  2"  to 
7",  by  eighths;  practice  being  slightly  different  for  each  com- 
pany. There  is  no  method  of  increasing  area  with  the  same 
grooves  as  in  angles,  Art.  20. 

Wire  is  found  in  the  cables  of  suspension  bridges,  while 
rounds  are  used  in  shafts,  in  rods  for  carrying  tension,  and  for 
making  bolts,  rivets,  pins,  and  rollers. 

Art.  19.    Rectangular  Shapes 

As  their  name  indicates,  these  have  a  rectangular  cross- 
section.  They  may  be  made  by  grooved  rolls,  by  flat  rolls,  or 
by  the  universal  mill  as  already  explained.  In  the  last  two 
cases  the  increase  in  thickness  is  made  by  simply  spreading  the 
rolls. 

A  rectangular  shape  which  has  its  width  and  thickness 
the  same  is  called  a  "square";  if  the  larger  dimension  is 
greater  than  eight  inches,  it  is  termed  a  "plate";  if  it  is  less, 
it  is  designated  a  "bar"  or  "flat,"  the  latter  term  being  usually 
applied  to  a  thin  section  less  than  three-sixteenths  of  an  inch 
in  thickness. 

Material  is  specified  thus,  2  Pis.,  36"Xi"X8'-4i",  the  first 
dimension  being  always  in  inches  and  parallel  to 
the  rolls.     In  this  case,  the  36"  dimension  would 
have  rolled  edges,*  the  others  being  sheared.     If 
FIG.  19.        above  mentioned  plate  is  irregular,  as  shown  in 
Irregular  Plate.  Fig.    1 9,   all  edges    are  sheared  edges.     This    is 
important  since  sheared  edges  do  not  make  a  nice 
fit  or  a  neat  appearance.     Moreover,  it  is  expensive  to  correct 

*  That  is,  it  would  if  rolled  in  a  universal  mill.  In  "sheared  plate"  it  is  rolled 
somewhat  larger  and  sheared  to  size. 


COMMERCIAL  SHAPES  31 

by  milling,  Art.  37.     As  already  noted  in  Art.  14,  the  thickness 
of  thin  plates  or  flats  is  often  given  in  gages. 

Common  sizes  are  about  as  follows.  Squares:  from  A" 
to  &"  by  32ds;  from  &"  to  2".' by  i6ths;  from  2"  to  3"  by 
eighths;  from  3"  to  5"  by  quarters.  Plates,  bars,  and  flats 
usually  vary  by  U.  S.  Standard  gages  where  less  than  \"  thick; 
above  that  to  2\"  in  thickness  by  sixteenths.  Above  15"  in 
width,  there  is  seldom  a  call  for  a  plate  more  than  one  inch  thick. 
Any  width  may  be  rolled  in  a  universal  mill,  or  may  be  sheared 
out.  Common  widths  run  from  2"  to  5"  by  half  inches;  5  to  12" 
by  inches;  12  to  36"  by  even  inches;  3  to  10  feet,  by  half  feet. 
These  shapes  in  their  different  forms  occur  frequently  in 
structural  work :  squares  are  used  for  ties;  diagonals  and  chords 
carrying  tension  only  are  often  made  of  bars;  plates  are  employed 
in^built-up  girders,  compression  members,  connection  plates, 
and  other  places  too  numerous  to  mention, 
^  .  •  . 

Art.  20.    Angles 

The  shape  of  the  minimum  thickness  of  an  angle  of  a  given 
length  of  legs  is  essentially  that  of  two  rectangles,  joined  together 
at  right  angles,  Fig.  200.  The  corners  on  the  inside  of  the 


FIG.  2oa. — Typical        FIG.  206. — Method  of  FIG.  2oc. — Method  of 

Angle.  Rolling.  Increasing  Section. 

angle  are  eased  by  curves  of  a  small  radius,  the  values  of  which 
may  be  found  in  the  handbooks.  These  curves  must  not  be 
forgotten  in  detailing. 

Fig.  206  shows  the  finishing  rolls  in  position  for  the  minimum 
thickness.  Let  the  unshaded  part  of  Fig.  2oc  represent  a 
4"X3"XA".  Then  ah  =  4",  he  =  $",  and  the  thickness  of 
either  leg  is  ft"-  Suppose  it  be  required  to  roll  a  4"X3"Xf". 
We  then  raise  the  rolls  an  amount  ai  =  ef=sec  45°  *X&"  =  |". 

*  Not  always  45°,  but  near  enough  for  illustrative  purposes. 


32  ELEMENTS  OF  STRUCTURAL  DESIGN 

The  distance  i%  =  ah  and  gf=he,  the  interior  lengths  and  radii 
remaining  unchanged.  It  will  be  noted,  however,  that  the 
extreme  length  of  each  leg  has  been  increased  by  &'  making 
the  real  size  4A"X3A"Xf",  although  it  is  spoken  of  as  a 
4"X3"Xi". 

This  theoretic  shape  is  modified  by  the  inaccuracies  of 
workmanship,  by  the  flowing  out  of  the  metal,  or  by  a  "  finishing 
pass."  The  above  reasons  make  the  length  of  the  leg  of  the 
angle  somewhat  uncertain;  hence,  in  design  and  detail,  we 
allow  for  a  possible  overrun.  For  the  same  reason,  dimensions 
perpendicular  to  the  edge  called  gages  are  always  given  from 
the  sharp  corner. 

An  angle  is  designated  by  the  length  of  each  leg  and  the 
common  thickness.  If  one  leg  is  longer  than  the  other,  it 
always  comes  first;  if  each  is  the  same,  both  must  be  given, 
thus: 

2Ls,6"X3i"Xi"X24'-61". 
iL,4"X4"   Xi"Xi'-o". 

Angles  are  sometimes  specified  by  weight,  but  both  weight  and 

thickness  should  never  be  given. 

Thus, 

iL,4"X4"Xi2.8#Xi'-o". 
Never, 

iL,  4"X4"Xi"Xi2.8#Xi'-o". 

In  the  handbooks,  angles  are  divided  into  equal  and  unequal 
legged,  although  the  same  general  principles  apply  to  each, 
and  they  are  equally  important.  They  may  be  obtained, 
increasing  by  small  amounts,  from  a  f"Xf"Xi"  to  an  8"X8" 
XiJ".  Regular  sizes  vary  only  by  sixteenths  of  an  inch  in 
thickness. 

Angles  are  very  common :  alone  or  with  2  or  4  riveted  together, 
they  may  be  used  for  small  tension  or  compression.  They  are 
employed  for  the  flanges  of  girders  and  stringers.  In  built  up 
columns  and  tension  members,  they  fasten  the  plates  together. 
These  are  but  a  few  of  their  many  applications. 


COMMERCIAL  SHAPES 


Art.  21.    I-Beams  and  Channels 

If  we  neglect  the  curves  which  are  used  instead  of  sharp 
angles  at  the  inside  corners,  an  I-beam  is  made  up  of  one  large 
rectangle  (the  web),  two  smaller  rectangles  and  four  triangles 
(the  flanges).  The  bevel  of  the  sloping  parts  is  2"  in  12"  for 
standard  sections.  See  Fig.  210. 

I-beams  are  rolled  horizontally  as  shown  in  Fig.  2ib.  In 
order  to  increase  the  weight  per  foot,  the  rolls  are  simply  spread 
farther  apart,  thus  changing  only  the  flange  width  and  web 


I 


FIG.  2i<z.  FIG.  2i&.  FIG.  2ic. 

Typical  I-beam.        Method  of  Rolling  I-beam.  Typical  Channel. 

thickness.  The  amount,  wr,  of  increase  in  pounds  per  lineal 
foot,  divided  by  the  height  in  inches  times  3.4,  equals  the  increased 
thickness  in  inches,  either  of  the  web  or  flange.  That  is, 


They  are  specified  by  their  depth  and  weight  per  foot,  thus, 

i/,  is"X4*#Xn'-4"; 

the  dimensions  of  the  American  standards,  adopted  January, 
1896,  are  thereby  understood.  The  sizes  vary  from  a  s"X$.5# 
to  a  24//Xioo#.  They  are  used  for  beams,  footings,  and  singly 
or  latticed  together  as  columns. 

The  Grey  process,  already  explained  in  Art.  17,  has  made 
possible  larger  Is  and  those  which  contain  more  material  in  the 
flanges  than  the  American  standard.  The  former  are  theoret- 
ically far  more  economical  either  for  a  column  or  for  a  beam  than 
the  latter.  If  the  ne,v  method  will  roll  as  good  a  quality  of 
steel  as  the  old,  it  will  extend  the  new  shapes  into  fields  hitherto- 
occupied  by  built-up  sections. 


34  ELEMENTS  OF  STRUCTURAL  DESIGN 

Cut  an  I-beam  in  two  along  the  web  and  we  have  a  channel, 
Fig.  2  ic.  Methods  of  rolling  and  increasing  the  section  are 
similar  to  those  for  I-beams. 

Channels  are  specified  by  their  depth  and  weight  per  foot, 
thus: 

4  [s,  i2"X2o.5#  Xso'-o". 

Sizes  vary  from  a  3"X4-o#  to  i5"X55#.  Shapes  some- 
what resembling  channels  are  employed  for  small  work  as  in 
expanded  metal  partitions.  Where  not  otherwise  stated,  the 
dimensions  of  the  American  standard  are  understood.  Channels 
are  used  for  columns  and  for  beams  in  places  where  an  I-beam 
is  not  so  convenient,  for  example,  against  a  wall. 

Art.  22.  Occasional  Shapes 

T  beams  are  composed  of  a  flange,  abc,  decreasing  in  thick- 
ness from  the  center,  and  a  stem,  bd,  increasing  towards  the  top, 


FIG.  220.  FIG.  226.  FIG.  22c.  FIG.  22d. 

Typical  T  beam.    Typical  Zee  bar.     Typical  Rail.          Typical  Trough  Section. 

Fig.  220.  There  is  no  method  of  enlarging  by  increasing  the 
distance  between  rolls. 

In  case  ac  equals  bd,  the  tee  is  called  equal  legged;  if  dif- 
ferent, unequal  legged.  They  are  best  designated  thus: 

2Ts,3"X4"X9.3#Xi2'-6", 

the  length  of  flange  always  being  given  before  the  depth  of 
leg.  Sizes  vary  from  a  i"Xi"Xi.o#  to  4i//X3i//Xi5-9#. 
They  are  used  principally  in  the  roofs  of  buildings. 

Zee  bars,  Fig.  226,  are  composed  of  three  rectangles  of 
the  same  thickness  with  some  of  the  corners  eased  as  shown. 
Methods  of  rolling  and  increasing  size  are  similar  to  those  for 
angles.  They  are  specified  thus, 

4  Zs,  3&"X5A"X3ft"Xf"  X24'-2". 


COMMERCIAL  SHAPES  35 

First  the  flange,  ab;  then  the  web,  ld\  next  the  flange,  de\  and 
last,  the  common  thickness.  It  will  be  noted  that  the  increase 
in  the  length  of  the  legs  is  shown,  differing  in  this  regard  from 
angles.  Since  the  two  flanges  are  usually  the  same,  one  of 
them  is  sometimes  omitted,  thus, 


Sizes  vary  from  a  3//X2^//Xi  to  a6i"X3f"X}".  Their 
principal  use  is  in  columns. 

Rails,  Fig.  22^,  of  many  different  kinds  are  rolled  but  the 
standards  of  the  American  Society  of  Civil  Engineers  are  usually 
specified,  as  they  may  be  more  readily  obtained.  Sizes  vary 
from  an  ij"  rail  at  8#  per  yard  to  a  6"  at  150$.  For  the 
Society  standards,  the  inclination  of  the  top  of  the  base  and 
the  bottom  of  the  head  is  13  degrees  with  the  horizontal.  It 
is  not  customary  to  spread  the  rolls  to  increase  the  weight. 


FIG.  226.  FIG.  22/.  FIG.  22g.  FIG.  2 2 h. 

Typical  Trough  Portion  of  Special  Typical 

Section.  Phoenix  Column.  Column.  H  section. 

Rails  are  specified  by  their  depth,  weight  per  yard,  and  name 
of  standard,  thus, 

10  Rails,  5"XSo#  per  yard,  A.S.C.E.,X3o'-o". 

The  depth  is  sometimes  omitted.  Rails  are  used  for  railroad 
tracks,  crane  tracks,  and  in  bearings  and  spread  footings. 

For  the  purpose  of  making  a  solid  steel  floor  with  sufficient 
strength  to  carry  a  load  for  a  span  of  several  feet,  special  shapes 
are  rolled,  so  designed  that  they  may  be  readily  fastened  together. 
See  Figs.  22 d  and  e.  Angles  and  plates  riveted  to  form  trough 
sections,  are  now  the  standard  construction  for  this  purpose, 
see  Vol.  II. 

Special  column  sections  are  rolled,  the  idea  being  to  obtain 
a  strong  post  with  a  minimum  of  riveting.  The  old  Phoenix 


36  ELEMENTS  OF  STRUCTURAL  DESIGN 

column  consisted  of  four  or  eight  shapes  fastened  together  as 
shown  in  Fig.  22f.  It  is  now  obsolete  on  account  of  the  dif- 
ficulty of  inspecting,  repainting,  and  making  connections  thereto. 
Jones  and  Laughlin  roll  a  patented  shape,  a  bent  I-beam,  which 
when  riveted  to  a  similar  shape,  give  us  a  post  as  shown  in 
Fig.  22g.  The  recently  introduced  H-shape,  Fig.  22/2,  has 
become  very  popular  as  a  column.  (Art.  56.) 

Pipes  are  sometimes  used  in  structural  work,  but  the  method 
of  manufacturing  them  does  not  belong  here.  Their  actual 
diameters  differ  somewhat  from  the  nominal,  and  tables  in 
handbooks  should  be  consulted  in  case  their  exact  dimensions 
are  required. 

Art.  23.    Rare  Shapes 

Among  such  may  be  mentioned  the  deck  or  bulb  beam, 
Fig.  230,  which  is  simply  an  I-beam  rounded  off  on  the  bottom. 
Manner  of  rolling,  of  increasing  weight,  and  of  specifying,  are 


FIG.  230.  FIG.  236.  FIG.  230. 

Typical  Bulb  Beam.  Typical  Bulb  Angle.  Typical  Splice  Angle. 

same  as  for  I-beams.  They  are  employed  in  place  of  the  latter 
on  ships. 

In  this  place  bulb  angles  are  also  used.  These  are  angles 
with  a  swelled  and  rounded  end,  as  shown  in  Fig.  236.  Manner 
of  rolling  is  same  as  for  angles. 

Angles  with  the  legs  at  more  or  less  than  ninety  degrees  may 
be  had,  but  it  is  generally  cheaper  to  bend  an  angle  or  plate 
to  the  required  shape. 

Splice  angles,  Fig.  23^,  which  are  angles  with  the  outside 
corner  rounded  so  as  to  fit  the  inside  of  an  angle,  may  be 
obtained;  but  it  is  preferable  to  plane  off  the  corner  and  shear 
the  edges  of  an  ordinary  angle. 


CHAPTER  III 


Attic 


WOODEN  STRUCTURES* 
Art.  24.    Principles  of  Design 

(1)  Timber  as  ordinarily  received  is  likely  to  be  a  little 
less  than  nominal  size. 

(2)  The  dimensions  of  timber  perpendicular  to  the  grain 
will  vary  with  the  amount  of  moisture  it  contains.     If  green 
timber  be  placed  in  a   warm  dry 

building,  it  will  shrink;  seasoned 
stuff  out-of-doors  will  absorb  moist- 
ure and  swell.  In  a  direction  par- 
allel to  the  grain,  there  is  little 
alteration.  (Art.  2.)  Hence,  where 
settlement  is  to  be  avoided,  put 
grain  of  timber  in  line  with  the 
loads.  If  some  pieces  must  be 
placed  otherwise,  make  them  as  thin 
as  possible.  For  example,  the  cracks 
in  the  plastering  of  dwelling  houses 
are  largely  due  to  unequal  settle- 
ment. This  is  caused  by  resting 
the  studs  on  top  of  the  joists,  Fig. 
240,  instead  of  passing  between 
them  as  in  Fig.  24^. 

(3)  When    practicable,    timber 

should  not  be  placed  where  it  will  be  subjected  to  alternations 
of  wet  and  dry.  This  is  in  order  to  prevent  wet  rot,  Art.  3. 
The  expense  of  roofing  wooden  bridges  has  been  considered 
advisable  in  many  instances  in  order  to  prolong  the  life  of  the 
structure. 

*" Structural  Details,"  by  H.  S.  Jacoby;  "Building  Construction  and  Super- 
intendence," Part  II,  by  F.  E.  Kidder;  "Architects'  and  Builders'  Pocket  Book," 
by  F.  E.  Kidder;  "Roof  Trusses  in  Wood  and  Steel,"  by  M.  A.  Howe. 

37 


_     l£  2.4a' 

Poor  Design. 


FIG.  246. 
Good  Design. 


Methods  of  Supporting  Floors  in 
Buildings. 


38 


ELEMENTS  OF  STRUCTURAL  DESIGN 


(4)  Keep  timber  well  ventilated  to  prevent  dry  rot.     (Art. 
3.)     If  it  be  necessary  to  build  a  member  of  two  or  more  pieces 
side  by  side,  they  should  be  held  an  inch  or  so  apart  by  blocks 
or  washers.     A  hole  is   sometimes  bored  lengthwise   through 
posts  with  crossholes  top  and  bottom,  partly  for  the  same  reason. 
The  bricking  up  of  the  ends  of  joists  or  trusses,  while  common, 
is  open  to  this  objection. 

(5)  Where  it  is  desirable  to  keep  out  the  rain,  arrange  joints 
so  that  water  would  be  compelled  to  run  up  hill  before  entering 
the  structure.     Thus,  in  the  cornice  shown  in  Fig.  24^,   instead 
of   details  in  24^,  we  may  employ  arrangement  of    24^.     How- 
ever, the  rain  which  drove  against  the  upright  board  would  still 
tend  to  follow  along  the  bottom  of  the  horizontal  board  and  into 


FIG.  246. 
Cornice. 


FIG. 
Incorrect. 


FIG.  246. 
Incorrect. 


FIG.  24/. 
Good. 


FIG.  24 
Good. 


Details  of  Cornice. 


the  wall.  To  prevent  this,  the  cornice  is  designed  as  shown  in 
Fig.  24/".  Another  method  is  to  cut  a  small  groove  on  the  under 
side  near  the  outer  corner  as  in  Fig.  24  g. 

(6)  The  exclusion  of  birds  and  vermin  must  be  borne  in 
mind  especially  in  residences  and  office  buildings.     Rat-proof- 
ing in  San  Francisco  is  now  compulsory.     Sparrows'  nests  in 
covered  Howe  trusses  are  a  frequent  cause  of  fire. 

(7)  A   structure   properly   designed   at   all   points   for   the 
usual  loads  is  reasonably  secure  against  hurricanes  or  earth- 
quakes.    In    localities    where    these    are    especially   prevalent, 
higher  values  should  be  assumed  for  the  wind  load  and  extra 
pains  should  be  taken  to  fasten  together  the  different  parts. 

(8)  To  protect  a  wooden  structure  from  fire: 

(a)  Avoid   small   sections.     A   io"Xio"  wooden  post  will 


WOODEN  STRUCTURES  39 

stand  a  fire  longer  than  an  unprotected  steel  beam  of  equal 
capacity. 

(b)  Keep  surfaces  as  unbroken  as  possible.    A  roof  made 
of  3"  plank  on  purlins  is  a  much  better  risk  than  one  of  i" 
boards  on  2"X8"  rafters. 

(c)  Avoid  enclosed  spaces,  for  the  fire  there  is  difficult  to 
reach. 

(d)  These  enclosed  spaces,  if  extending  from  floor   to  floor, 
are  even  more  objectionable  as  they  help  the  spread  of  flames. 

(9)  The  strength  of  the  wood  in  bearing  perpendicular  to 
the  grain  is  much  smaller  than  its  compressive  strength.  A 
column  is  frequently  designed  as  shown  in  Fig.  24/f.  However, 


FIG.  24/1.  FIG.  241.  FIG. 

Post  with  Bolster.     Cast-iron  Base.      Splice  at  Base. 

except  for  very  long  columns,  the  bolster  is  much  the  weaker 
part.  This  may  be  remedied  by  making  the  latter  of  strong 
material,  white  oak  for  example.  Also  a  casting  as  shown  in 
Fig.  241  may  be  used  or  bolster  and  column  spliced  as  in  Fig.  247. 
(10)  Lack  of  strength  in  shearing  along  the  grain  is  perhaps 
its  most  important  characteristic,  weakening  it  much  as  a 
structural  material.  In  splicing  or  joining  a  tension  member, 
this  fault  makes  it  possible  to  secure  but  a  fraction  of  the  orig- 
inal strength.  For  the  same  reason  notching  a  beam  either 
top  or  bottom,  produces,  especially  when  near  the  ends,  a  large 
loss  in  capacity. 


40  ELEMENTS  OF  STRUCTURAL  DESIGN 

Art.  25.    Accessories  of  Other  Material 

Steel,  wrought  iron,  and  cast  iron  are  valuable  aids  in  the 
design  of  wooden  structures.  In  this  article,  when  not  other- 
wise mentioned,  either  of  the  first  two  may  be  used. 

(i)  Tension  Members.  For  the  reason  given  in  (10)  of 
preceding  article  and  also  that  in  Art.  27,  iron  finds  frequent 
application  in  the  transmission  of  tension.  Fig.  25^  shows 
how  a  rod  may  be  used  for  this  purpose.  The  bearing  area  at 
the  notch  should  have  a  strength  equal  to  that  of  the  rod.  If 
in  addition,  the  latter  be  upset,  Art.  43,  its  full  strength  will 
be  conserved.  In  upsetting,  the  blacksmith  enlarges  each  end 
of  the  rod  until  the  excess  is  sufficient  to  provide  for  the  cutting 
of  the  thread  and  the  weakening  due  to  forging.  Dimensions 


FIG.  250. — Use  of  Rod        FIG.  256.        FIG.  25^,  FIG.  2$d. — Hangers, 
as  Tension  Member.        Upset  End. 

of  upsets  can  be  obtained  from  handbooks.  It  does  not  pay 
if  the  pieces  be  short,  small,  or  few  in  number.  Fig.  25^  shows 
an  upset  with  a  thread  turned  thereon.  Eyebars,  Art.  43, 
or  loop  rods,  Art.  42,  may  also  serve  as  tension  members.  In 
either  case,  pins,  large  special  bolts,  Art.  46,  are  used  at  the 
joints. 

(2)  Connection  Plates.     These  are  usually  plates  or  bars, 
either  bent  or  straight.     Some  will  be  taken  up  in  later  articles 
in  this  chapter.     Of  the  many  useful  applications,  we  will  call 
attention  to  the  hanger,  which  may  be  found  where  one  beam 
frames  into  another  at  right   angles.     Fig.  2$c  shows  the  single 
type;    25^,  the  double.     The  twist  should  be  so  made  that   the 
upper  parts  of  the  hangers  lie  flat  against  connecting  beam. 
The  size  of  the  bar  varies  from  2ffX\"  to  4"Xf".     The  strap 
bolt,  Fig.  26u,  is  another  excellent  form. 

(3)  Reinforcement    for    Beams.      For    example,    Fig.    250 
shows  the  manner  in  which  the  steel  is  placed  in  a  "  flitched  " 


WOODEN  STRUCTURES  41 

beam.  Plate  should  be  f  to  f"  thick;  the  total  width  of  the 
timber,  about  twelve  times  that  of  the  plate;  the  plate,  \" 
less  depth  than  the  wood  on  account  of  overrun  of  steel  and  under- 
run  and  shrinkage  of  timber.  An  alternate  spacing  of  18" 
suffices  for  the  I"  bolts. 


FIG.  25^. — Flitched  Beam. 

(4)  Bearing  Blocks.  These  are  usually  of  cast  iron.  Their 
function  is  to  distribute  the  pressure  over  a  larger  area  of  masonry 
or  timber.  The  latter  case  has  already  been  discussed  in  (9) 
of  the  preceding  article.  Fig.  242  in  that  paragraph  represents 
one  type  of  a  bearing  block.  A  style  known  as  the  angle  block 
is  shown  in  Fig.  262.  Still  another  angle  block  is  seen  in  Fig.  31  d. 


FIG.  25/f.         FIG.  25*. 
Washers. 

(5)  Washers.    The  ratio  of  the  bearing. strength  of  timber 
perpendicular  to  grain  to  that  of  iron  is  very  roughly  one-twenty- 
fifth.     If  we  allow  for  the  screw  thread,  we  find  that  about 
fifteen  times  gross  area  of  rod  is  required  in  bearing.     As  this 
is  an  extreme  case,  standards  are  often  a  little  less.     For  bolts 
where  they  are  not  in  tension,  full  development  is  not  necessary. 
Here  the    plate  washer,  Fig.  257,  or  square  washer,  Fig.  25^, 
suffices.     Either  may  be  cast  with  a  cored  hole  or  made  of  rolled 
stuff  with  a  punched  hole.  At  any  rate  it  should  be  J"  greater 
than  threaded  end.     The  diameter  of  the  washer  is  two  or 
three  times  that  of  the  bolt.     The  thickness  must  not  be  less 
than  J".     The  remaining  washers  are  cast.      Fig.   257'  shows 
an  ogee  washer,  a  very  common  form.     Its  thickness  equals 
diameter  of  bolt  equals  one-half  diameter  at  top  equals  J  diameter 
at  bottom.     Fig.  2$h   represents  a  lighter  form,  while  Fig.  25^ 
gives  a  washer  where  the  rod  enters  at  an  angle. 

(6)  Keys.     These,  are  simple  prisms  of  a  uniform  rectangular 


42  ELEMENTS  OF  STRUCTURAL  DESIGN 

section,  usually  of  cast  iron.     However,  they  may  be  made  of 
some  wood  which,  like  oak,  possesses  a  large  resistance  to  shear. 
Fig.  26k  exemplifies  their  use. 
(7)  Fastenings. 

(a)  Nails,   either   cut   or  wire,   are   familiar   to   all.     They 
are   specified   as   twopenny  (2d);    threepenny  (3d);    etc.,  sizes 
varying  from  2d  to  6od.     Dimensions  are  given  in  handbooks. 

(b)  Bolts.     These  are  rounds  with  one  end  headed  up  and 
a  thread  turned  on  the  other.     The  head  is  a  prism  either 
square  as  in  Fig.  25^,  or  hexagonal.      On   the  threaded  end  is 
placed  a  nut  which  also  may  be  either  square  or  hexagonal. 
Bolts  are  specified  by  diameter  of  cylindrical  part  and  length 
/,  Fig.  25^,  thus,  240  bolts,  f"X6"  u.h.,   (under    head)  with 
square  heads  and  nuts.     Usual  sizes  of  bolts  are,  J,  f,  i,  ij,  \\" 
diameters.     Up  to   24"  in  length,   they  are  carried  in  stock. 
Holes  in  wood  are  usually  made  the  same  size  as  the  bolt. 


FIG.  25^.  FIG.  25^.  FIG.  257?*.  FIG.  257*. 

Bolt.  Lag  Screw.         Wood  Screw.         Drift  Bolt. 

(c)  Lag  screws  are  bolts  with   the  screw  end  pointed,  but 
without  nuts   (Fig.   25/).     They  vary  in  size  from  JXi|"  to 
1X12"  u.h. 

(d)  Wood   screws,  Fig.  25^,  are   somewhat   similar  except 
that  the  head  is  differently  shaped  and  has  a  slot  for  driving. 
They  are  made  in  all  sizes  up  to  6"  in  length. 

(e)  Drift  bolts,  Fig.  25^,  look  very  much   like   large  spikes 
and  are  driven  in  a  similar  way  into  a  bored  hole.    The  diam- 
eter of  the  round  hole  should  be  30  per  cent  less  for  the  round 
bolt   and   15  per  cent  less   for  the  square.     Ragging,  that  is, 
roughening  the  bolt,  lessens  its  holding  power. 

(/)  Dowels  or  dowel  pins  are  double-ended  drift  bolts. 

Art.  26.    Joints 

While  almost  any  joint  may  be  made  entirely  of  timber, 
it  will  be  generally  possible  to  conserve  a  large  percentage  of 
the  original  strength  only  by  the  use  of  steel. 


WOODEN  STRUCTURES 


Where  the  members  are  fastened  together  by  overlapping 
and  bolting  as  in  Fig.  260,  it  is  called  a  scarf  joint. 

A  fish  joint  is  one  where  the  members  abut  and  are  fastened 
together  at  the  side  by  timbers  or  plates  called  fish  plates. 

Let  us  take  now  the  very  simple  fish  joint  shown  in  Fig.  266, 


FIG.  26a. — 
Scarf  Joint. 


FIG.  26b. 

±_    1J    ill  Fish  Joint. 


FIG.  26c. 


FIG. 


FIG.  266, 


FIG.  26f. 


SSJ  S,'  =  shearing  unit  stresses  of  timber  and  metal  respectively. 
St,  St'  =  tensile  unit  stresses  of  timber  and  metal  respectively. 
Sfj  S/  flexural  unit  stresses  of  timber  and  metal  respectively. 
S&f,  S6/= bearing  unit  stresses  of  metal  against  timber  and  metal 
respectively. 


44  ELEMENTS  OF  STRUCTURAL  DESIGN 

;  The  true  distribution  of  loads  on  the  bolt  with  the  diagram 
of  bending  moments  is  given  in  Fig.  26c.  Fig.  26d  represents 
our  assumption;  Fig.  260,  that  usually  employed.  The  latter 
arrangement  gives  much  higher  bending  stresses  than  either  of 
the  other  two.  To  neutralize  this,  it  is  common  to  employ  high 
ilexural  stresses  in  connection  with  such  assumption.  Let 
us  now  investigate  the  safe  capacity  of  such  a  bolt,  using  Fig. 
26^.  Here  the  bolt  of  diameter  d  will  be  loaded  with  the  safe 
bearing  pressure  for  such  a  distance  /  that  the  safe  shearing  or 
ilexural  strength  is  equaled.  This  distance  /  must  not  exceed  / 
in  Fig.  266.  By  equating  shear  and  moment  to  the  resistance 
of  the  section  of  the  bolt  we  obtain  : 
For  shear 

/=ic<J 
For  moment 


Fig.  26/  shows  the  forces  where  the  steel    fish  plates  are 
used.     Here  above  equations  become, 


By  these  equations  the  safe  lateral  resistance  in  pounds 
may  be  computed  for  a  one-inch  round  bolt,  drift  bolt,  spike, 
nail,  wood  screw,  or  lag  screw.  Other  sizes  will  carry  a  load 
in  proportion  to  the  diameter  squared.  For  double  shear, 
double  values.  We  have  also  added  safe  unit  resistance  to 
withdrawal.  For  screws  this  is  based  upon  the  area  of  the 
circumscribing  cylinder.  In  nails  and  screws,  area  of  the  point 
is  not  considered.  The  quantities  given  are  for  buildings,  for 
bridges  use  two-  thirds  of  same.  Amounts  below  are  based 
upon  proper  design  of  e,  p,  and  t,  Fig.  266. 

This  distance  e  should  be  such  that  the  safe  shearing  stress 
is  not  exceeded.  Assume  this  to  be  carried  in  the  same  depth 
as  the  bearing, 


or 


a  mean  value  of  which  is  6d  for  pressure  parallel  to  grain. 


WOODEN  STRUCTURES 


45 


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46 


ELEMENTS  OF  STRUCTURAL  DESIGN 


On  account  of  washer  and  nuts,  p  cannot  be  much  less  than 
3^,  Art.  25  (5).  As  in  riveted  joints,  the  idea  is  to  make  strength 
of  bolts  equal  to  that  of  the  net  section.  Economy  of  material 
for  a  tension  joint  may  be  promoted  by  arranging  it  as  shown 
in  Fig.  26g. 

Above  analysis  gives  uniform  weight  of  bolts,  no  matter 
what  diameter  may  be  taken.  Hence  use  as  large  a  size  as  is 


!  FIG.  26g.— Efficient  Joint.     FIG.  26^.— Fish.        FIG.  261— Scarf. 
Joints  for  Compression  Members. 

convenient  and  will  afford  a  satisfactory  distribution  of  the 
stresses. 

We  will  now  consider  the  following  cases: 

(1)  Splicing  a  compression  member. 

(2)  Splicing  a  tension  member. 

(3)  Splicing  a  beam. 

(4)  A  tension  member  entering  a  piece. 

(5)  A  compression  member  entering  a  piece. 

(6)  A  beam  framing  into  another  beam. 

(i)  Compression  members  may  be  spliced  by: 

(a)  Fish  plates .  on  alt  four  sides,   Fig.   26h.     Each  plate 
should  have  not  less  tnan  two  rows  of  not  less  than  two  bolts 
each  on  each  side  of  joint. 

(b)  Scarf  joint  which  should  be  parallel  and  perpendicular 
to  the  compression  as  shown  in  Fig.  2 6i. 

(c)  Combination  of  the  two. 

Abutting  surfaces  are  supposed  to  carry  the  load  and  the 
bolts  are  put  in  to  render  the  member  continuous  under  com- 


WOODEN  STRUCTURES 


47 


pression.    Properly  built  joints  have  an  efficiency  close  to  100 
per  cent. 

(2)  Tension  members  are  spliced  by: 

(a)  Plain  joint  with  2  or  4  fish  plates,  either  of  timber  or 
steel.     Fig.  26b  would  do  for  small  tensile  stresses. 

(b)  Scarf  joint,  Fig.  26;. 

(c)  Combination  of  fish  and  scarf,  often  with  keys,  Fig,  26k. 


FIG.  26;.— Scarf  Joint  for  Tension. 

(d)  Fish  plates  if  of  steel  may  be  bent  and,  if  of  timber,  may 
be  notched  into  the  tie.  Fig.  261  shows  the  latter  case. 

The  author  prefers  (a).  It  should  be  remembered  that  the 
notching  and  fitting  of  complicated  joints  are  expensive.  Some 


FIG.  26k. — Combination  Joint  for  Tension. 


FIG.  261.— Notched  Fish  Plate  Joint  for  Tension. 


of  these  may  show  higher  efficiency  in  an  analysis  based  on 
all  elements  working  in  unison.  This,  however,  is  an  ideal 
which  is  not  reached  in  practice.  For  example,  in  Fig.  26k, 
it  is  quite  difficult  to  notch  out  so  exactly  that  the  load  will 
be  divided  among  the  keys  and  bolts  in  proportion  to  their 
strength. 

To  illustrate  the  computation  of  a  joint  in  tension,  let  us 


ELEMENTS  OF  STRUCTURAL  DESIGN 


determine  the  capacity  of  splice  shown  in  Fig.  26k.  Timber, 
white  oak;  cast  iron  keys;  and  i"  steel  bolts.  Piece  is  8"X8", 
hence  will  have  two  rows  of  bolts.  Using  stresses  for  buildings, 
these  two  rows  of  five  bolts  each  will  carry, 

10X2X1  500  =  30000  Ibs. 

The  maximum  stress  on  the  net  section  of  the   2jX8"-fish 
plate  occurs  at  a,  and  is, 

i5,ooo/(2^X6)  =  iooo  Ibs.  per  sq.in.  O.K. 


Taking  the  keys  as  i"  in  width,  the  capacity  of  each  is, 
8X7X150  =  8400  Ibs. 

Half  depth  of  key  must  be  such  that  allowable  bearing  is 
not  exceeded.  9 

8400/8  X  1  500  =  0.70  in. 

We  will  make  them  ij"  deep.     The  total  capacity  of  the 
joint  is  then, 

30000+16800  =  46800  Ibs. 

To  obtain  this  capacity,  fish  plates  must  be  extended  to 

include  four  more  rows  of  bolts  to 
the  right  of  the  upper  a  and  to 
the  left  of  the  lower  one. 

(3)  Splicing  for  bending  is  to 
be  avoided  where  possible.  If 
necessary,  use  methods  given 
in  (2).  As  before,  (a)  is  preferable. 
The  plates  may  be  planes  parallel 

FIG.  26«.-Joint  in  BeanTwith  Steel  to  the  moment  or  in  planes  per- 

Fish  Plates.  pendicular  thereto.    In  the  former 

case,   they   must    be    treated   as 

shown  in  Art.  59  provision  being  made  for  the  fact,  that 
the  resultant  pressure  for  some  of  the  bolts  is  not  parallel 
to  the  grain.  To  illustrate  the  latter  case,  let  it  be  required  to 


WOODEN  STRUCTURES 


49 


splice  a  10X10"  spruce  for  a  building  to  conserve  the  strength 
of  the  net  section,  taken  as  8X10",  Fig.  26m.  Allowable 
bending  moment  is, 


Let  us  make  plates  and  bolts  of  steel.    For  the  former  we  will 
require, 

100000/10X16000=0.62  sq.in. 

We  will  use  10X3/8"  plates,  furnishing  2.91  sq.in.  net  area. 


FIG.  26w. — Mortise, 
and  Tenon  Joint. 


FIG.  260.— Fish 
Joint. 


FIG.  26p. — Joint  with 
Bent  Connection  Plate. 


The  stress  in  the  plate  equals  100,000/10  equals    10,000  Ibs. 
Number  of  i"  bolts  required  is, 

10000/1900  =  6, 

arranged  as  shown  in  Fig.  26m.    The  bolts  at  d  should  be  inserted 
to  prevent  the  buckling  of  the  plate  in  compression. 

(4)  A  joint  where  a  tension  member  enters  a  piece  may  be 
handled  by : 

(a)  Mortise  and  tenon  joint,  Fig.  26^.      This  is  expensive 
and  lacks  strength  as  an  analysis  will  show. 

(b)  Plain  fish  joint,  Fig.  260.     This  joint  is  objectionable 
on  account  of  the  weakness  of  the  bolts  which  are  in  bearing 
almost  perpendicular  to  the  grain  and  the  tendency  to  split 
the  horizontal  piece. 

(c)  A  rod  as  given  by  Fig.   250.     This  is  a  good  detail. 
Where  bearing  is  inclined,  allowable  values  may  be  interpolated 
according  to  the  inclination  in  degrees  as  shown  in  the  example 
below. 


50 


ELEMENTS  OF  STRUCTURAL  DESIGN 


(d)  Bent  strap  of  iron  or  steel  as  represented  in  Fig.  26p. 
This  is  also  an  excellent  detail. 

Let  us  exemplify  computations  by  designing  rod  in  Fig. 
2$a  to  carry  10,000  Ibs.  when  used  for  a  roof  truss  of  wrought 
iron  and  yellow  pine.  The  size  of  the  rod  is 

iuJ2/4  =  10000/12000  =  0.83  sq.in.     Use  ITS"  dia.  round  rod. 

Taking  inclination  of  rod  with  horizontal  as  60  degrees. 
Allowable    bearing    pressure  =  600 +(900X30) /go  =  900    Ibs. 
per  sq.in. 

Area  required  =  10000/900  =  11.1  sq.in. 
An  ogee  washer  4"  in  diameter  might  be  used. 
(5)  Where  a  strut  enters  a  piece,  the  compression  may  be 
taken  by : 

(a)  Notching,  Fig.  26*7  and  r.  The  former  is  the  proper 
design  for  small  stresses,  acting  at  an 
inclination.  It  should  be  nailed  in.  Fig. 
26r  has  the  weakness  spoken  of  in  Art. 
24  (9),  and  may  be  strengthened  as  there 
noted. 

(b)  Where  there  is  little  or  no  hori- 
zontal component,  the  notching  may  be 

omitted.     The  strut  is  then  held  in  place  by  toenailing  or  drift 
bolts. 

(c)  Bolting  on  an  additional  piece    as  shown  in  Fig.  265. 


FIG.  26q.        FIG.  26r. 
Notched  Joints. 


FIG.  26s.  FIG.  261.  FIG.  26«.  FIG.  26v. 

Methods  for  Carrying  Compression  at  an  Angle. 

(d)  Bolting  inclined  piece  as  represented  in  Fig.  26*.     A 
somewhat  similar  scheme,  employing  the  strap  bolt,  is  given 
in  Fig.  2614. 

(e)  The  use  of  cast  or  wrought-iron  shoes.     See  Fig.   261) 
and  3  id.      This  is  probably  the  best  method  for  large  stresses. 


WOODEN  STRUCTURES  51 

Combinations  of  several  types  are  frequent.  However,  as 
already  pointed  out,  there  is  difficulty  in  making  different 
parts  work  together. 

As  an  example  of  the  computations  for  these  joints,  let  us 
consider  Fig.  26q  when  built  in  red  oak  for  a  railroad  bridge. 
Let  the  inclined  member  be  a  6"X6"  at  an  angle  of  30°  with 
the  horizontal,  and  let  its  stress  be  12,000  Ibs.  Its  horizontal 
component  is  then  10,500  and  vertical  6000.  At  650  and  350 
Ibs.  per  square  inch  respectively,  there  are  required  16.1 
and  17.1  sq.in.  The  depth  of  the  notch  must  then  be  2j", 
while  the  length  of  inclined  bearing  should  be  not  less  than  3" '. 
A  more  exact  method  is  indicated  in  Fig.  2ge. 

(6)  A  beam  framing  into  another  beam,  usually  at  right 
angles.  There  are  three  common  methods : 

(a)  Mortise  and  tenon,  similar  to  Fig.  26n. 

(b)  Toenailing  (nailing  on  side). 

(c)  Hangers.    Two  representatives  of  one  type  are  shown  in 
Fig.  25*;  and  d. 

(a)  is  expensive  and  weak,  (b)  is  cheap  and  weak,  while 
(c)  is  expensive  but  strong,  conserving,  when  properly  designed, 
the  full  strength  of  both  beams. 

One  of  the  best  methods  is  to  use  a  built-up  section.  For 
example,  an  8"X8"  timber  may  be  made  from  planks,  each 
2X8"Xi6'-o"  securely  bolted  together  with  one  joint  every 
.4  feet.  With  good  abutting  joints  this  should  be  as  strong  as 
an  8"X8"  in  compression.  In  tension  it  should  have  a  net  area 
of  about  6"X6".  Also  joints  (4)  and  (5)  may  be  designed  by 
making  one  member  double  and  passing  the  other  through  it. 

Art.  27.    Design  of  Timber  Structures 

The  objects  of  design  are: 

To  provide  a  structure  safe  under  any  probable  circumstances. 
To  do  this  as  economically  as  possible. 
The  latter  is  fulfilled  by  making  the  sum  of  the  following 
annual  charges  a  minimum : 

(a)  Interest  on  first  cost. 

(b)  Maintenance. 


52 


ELEMENTS  OF  STRUCTURAL  DESIGN 


(c)  Sinking  fund.     At  the  expiration  of  the  life  of  the  struc- 
ture, this  fund  must  be  sufficient  to  rebuild  it. 

(d)  Operation. 

Suppose  two  alternative  schemes  proposed  for  a  drawbridge 
to  be  as  follows:  No.  i  will  cost  $200,000;  repairs,  painting,  and 
so  forth,  $400  per  year;  bridge  is  estimated  to  last  30  years;  it 
will  be  operated  by  9  men  at  a  total  cost  of  $20  per  day.  For 
Scheme  No.  2,  the  corresponding  quantities  are:  cost,  $150,000; 
repairs,  $300;  duration,  25  years;  operation,  12  men,  $27. 
Taking  masonry  as  alike  in  both  cases  and  interest  at  4%,  we 
may  compare  as  follows: 


Scheme. 

a. 
Interest. 

b. 
Maintenance. 

c. 

Sinking    Fund. 

d. 
Operation. 

Total  Annual 
Charge. 

I 

$8000 

$400 

$3560 

$7300 

$19,260 

2 

6000 

300 

3600 
See  Trautwine, 
p.  46. 

9850 

19,750 

Our  analysis  shows  a  slight  preference  for  No.  i. 

It  is  necessary  for  a  student  to  obtain  an  elementary  knowl- 
edge of  many  subjects  and  time  can  seldom  be  afforded  for 
alternative  designs.  However,  in  practice,  several  should  be 
drawn  up  on  detail  paper  and  thoroughly  examined  to  eliminate 
all  wraste  and  weaknesses.  Then,  after  comparison  of  costs  as 
above  outlined,  the  best  is  selected  for  the  finished  drawing  of 
the  proposed  structure. 

To  compare  wood  and  iron,  let  us  take  their  cost  when 
fabricated  at  $50  per  M  and  3  cents  per  pound. 

1  sq.in.  of  iron  will  carry  12,000  Ibs.  tension  and  will  cost 
10  cents  per  foot. 

27  sq.in.  of  wood  will  carry  12,000  Ibs.  tension  and  will 
cost  ii  cents  per  foot. 

2  sq.in.  of  iron  will  carry  12,000  Ibs.  compression  and  will 
cost  20  cents  per  foot. 

15  sq.in.  of  timber  will  carry  12,000  Ibs.  compression  and 
will  cost  6  €ents  per  foot. 

The  above  is  quite  rough  since  allowance  has  to  be  made 
for  excess  of  gross  over  net  area,  the  reduction  of  allowable 
stress  in  compression,  and  so  forth.  It  indicates  clearly  why 


WOODEN  STRUCTURES  53 

wood  is  cheaper  than  iron  in  first  cost  and  also  why  the  latter 
is  often  employed  in  tension  members. 

In  the  preceding  articles,  iron  has  been  freely  used  in  framing 
joints.  Its  shearing  and  bearing  strength,  large  as  compared 
with  wood,  make  it  particularly  valuable.  The  objections 
are: 

(1)  It  is  largely  blacksmith's  work  and  therefore  expensive. 
(Art.  42.) 

(2)  Small  pieces  are  likely  to  be  lost  in  shipping.     (Art.  48.) 

(3)  In  the  case  of  error  or  change  in  design,  iron  is  not 
as  easy  to  alter  as  timber. 

(4)  Another   material   adds   to   the   difficulty   of   handling 
the  job.     However,  its   advantages  are   such  that   it  is  used 
considerably. 

If  much  framing  is  required  and  the  timbers  are  small, 
spruce,  white  pine,  Norway  pine,  or  hemlock  may  be  employed. 
All  frame  easily  but  the  latter  is  often  weak  and  treacherous. 
For  heavy  pieces  and  small  amounts  of  notching  and  cutting, 
use  yellow  pine  and  white  oak.  These  are  strong  woods  but 
they  frame  with  some  difficulty.  For  long  pieces,  take  yellow 
or  (Jregon  pine.  Sleepers  and  posts  are  made  of  cedar,  chestnut, 
and  cypress.  Keys  and  fish  plates,  if  of  wood,  are  commonly 
of  white  oak.  . 

On  account  of  the  rule  that  safety  of  the  structure  must 
not  depend  upon  friction,  bolts  and  screws  make  a  much  better 
design  than  spikes  or  nails.  One  of  the  former  must  be  used 
when  in  direct  tension  and  they  are  preferable  in  shear.  Drift 
bolts,  dowel  pins,  and  nails  may  be  employed  where  the  stress 
is  carried  mainly  in  bearing.  A  cheap  and  rapid  method  for 
temporary  construction  is  the  fastening  together  by  spikes. 
A  disadvantage,  particularly  with  wire  spikes,  is  the  lessened 
salvage  value.  Lag  screws  are  difficult  to  drive  in  hard  woods 
like  oak. 

In  Europe,  labor  is  cheap  and  lumber  dear,  hence  elaborate 
joints  are  often  made  to  save  material.  Here  the  reverse  is 
true,  therefore  plain  joints  with  ample  connecting  plates  are 
economical. 

Ties  exposed  to  the  wind  and  compression  members  must 
be  thoroughly  braced.  It  is  sometimes  necessary  to  use  knee 


54 


ELEMENTS  OF  STEUCTURAL  DESIGN 


X 


bracing,  Fig.  270,  but  it  is  not  as  strong  as  the  X  bracing  in 
Fig.  2jb,  and  it  introduces  large  bending 
stresses.      Well-nailed   boarding   is    con- 
sidered equivalent  to  an  X  bracing  in  its 
FIG  270          FIG  276     plane-     It  is  much  more  efficient  if  laid 

Knee  Bracing.     X  Bracing,    diagonally. 

It  is  customary  to  make  no  provision 

for  the  alteration  of  length  of  timber  with  change  of  tempera- 
ture and  to  neglect  consideration  of  the  stresses  caused  thereby. 


Pole 


FIG.  280. 


Art.  28.     General  Description  of  Roof  Trusses 

Underneath  the  slate,  shingles,  or  other  covering,  lies  the 
boarding,   running   parallel   to   the   peak.     This   boarding,    or 
sheathing,  as  it  is  sometimes  called,  is  planed  on  one  side  and 
nailed  to  the  raf- 
ters   which    sup- 
port it,  Fig.   286.' 
The    latter    are 
"sized,"  that  is, 
are     notched    a 
small  amount,  to 

FIG.  286.  V 


bring  their  tops 
to  a  uniform  level 
over  the  purlins. 
These  are  beams 
running  parallel 
to  the  peak  in 
turn  resting  on 
the  trusses.  They  are  preferably  placed  vertically  or  perpen- 
dicularly above  the  joint  in  the  truss  on  which  they  rest. 
If  otherwise  located,  top  chord  must  be  computed  to  carry  the 
combined  compression  and  bending. 

Another  method  is  to  run  the  boarding  perpendicular  to 
the  peak  and  to  rest  it  directly  upon  the  purlins,  omitting  the 
rafters.  Although  more  material  will  be  used  this  way,  it 
requires  less  work  and  is  a  better  fire  risk,  Art.  24,  (8),  (a)  and 
(b).  Or  both  purlins  and  rafters  may  be  omitted  and  sheath- 
ing run  directly  from  truss  to  truss,  resting  on  the  top  chord. 


FIG.  28c. 
Typical  Arrangement  of  Roof  Truss. 


WOODEN  STRUCTURES  55 

The  thickness  of  the  boarding  varies  from  f"  to  3";  it  is 
often  assumed  and  allowable  span  computed.  This  should  be 
such  that  deflection  is  not  more  than  0.2  per  cent  of  the  same. 
This  condition  will  be  fulfilled  by  making  ratio  of  span  to  thick- 
ness not  more  than  30.  The  rafters  are  usually  2X4",  2X6," 
or  2X8,"  with  larger  dimension  vertical.  8X8",  8Xio"r 
and  10X10"  are  common  for  the  purlins,  the  latter  in  each  case 
being  perpendicular  to  the  roof.  Two  purlins  are  used  at  the 
peak,  one  on  each  side,  Fig.  280.  They  have  the  same  depth  as. 
the  others  but  only  i  to  f  the  width  on  account  of  the  lessened 
load.  At  this  place,  it  is  customary  to  insert  between  the  rafters 
the  ridgepole.  It  is  made  a  -little  deeper  to  ensure  full  bearing 
and  2"  thick.  At  the  eaves  where  the  truss  meets  the  wall, 
the  rafters  are  notched  over  a  piece  called  the  plate  which  lies 
horizontally.  They  are  then  extended  to  support  the  gutter 


FIG.  2Sd.  FIG.  2&e.  FIG.  28/.  FIG.  28g. 

Forms  of  Roof  Trusses. 

and  the  finish  around  it,  the  three  together  constituting  the 
"  cornice,"  Fig.  28^.  If  this  plate  rests  upon  the  brickwork, 
it  is  made  of  sufficient  size  to  distribute  the  load  over  the 
masonry.  A  4X8"  laid  flat  would  do.  In  the  design  of  the 
cornice,  care  should  be  taken  to  provide  enough  waterway  and 
to  exclude  weather  and  rain  from  the  building. 

The  purlins  usually  extend  over  a  single  "  bay,"  as  the 
distance  center  to  center  of  trusses  is  called.  This  should  be 
chosen  to  utilize  some  stock  length  of  timber,  such  as  n'-6" 
to  use  12'  stuff,  i3'-6",  i5'-6",  etc.  It  may  be  determined 
by  conditions  within  the  building,  such  as  location  of  windows 
in  supporting  wall.  When  there  is  no  such  limitation,  several 
different  lengths  may  be  tried,  the  cost  of  roof  trusses  esti- 
mated and  the  most  economical  chosen.  This  is  usually  about 
15  feet  decreasing  somewhat  for  small  spans.  In  a  like  way  the 
most  efficient  arrangement  for  rafters,  purlins,  and  trusses  may 
be  investigated. 

Figs.  28  d,  e,  f,  and  g  show  types  of   wooden  roof    trusses; 


56  ELEMENTS  OF  STRUCTUKAL  DESIGN 

/  representing  what  is  perhaps  the  most  common  one.  Light 
lines  indicate  those  members  which  are  usually  made  of  iron 
in  combination  trusses,  that  is,  in  trusses  made  of  iron  and  tim- 
ber. However,  all  tension  members  are  sometimes  made  of 
steel  or  iron.  Like  the  roof  systems,  various  trusses  may  be 
tried  to  secure  the  most  favorable  design.  Most  economical 
inclination  is  one- third  pitch,  that  is,  making  the  ratio  of  height 
at  center  to  span  one- third. 

Bracing  is  usually  omitted  where  the  truss  rests  on  brick 
walls.  In  this  case  the  sheathing  is  supposed  to  give  sufficient 
stiffness.  Where  trusses  rest  on  isolated  columns,  the  latter 
must  be  braced  both  ways.  X  bracing  is  best>  but  knee  bracing 
is  often  used  on  account  of  the  clearance  required. 

The  dead  weight  per  inclined  square  foot  for  various  kinds 
of  roofing  exclusive  of  sheathing  is  about  as  follows:  Shingles, 
2  to  3  Ibs.;  slate,  5  to  8;  tiles,  10  to  40;  tin,  i  to  2;  corrugated 
iron,  i  to  3;  gravel,  6  to  8.  The  weight  of  timber  per  foot 
B.M.  (board  measure)  may  be  estimated  as,  oak,  4.5.  Ibs.; 
hard  pine,  4;  cedar,  cypress,  hemlock,  spruce,  and  chestnut, 
3;  white  pine  and  poplar,  2.5.  The  weight  in  pounds,  W, 
of  the  truss  alone  may  be  obtained  from  Jacoby's  formula: 

W  =  o.$  as  (1+0.155). 

Here  a  is  the  length  of  bay  while  5  is  the  span,  both  in  feet. 
The  weight  of  snow  in  pounds  per  horizontal  square  foot,  w, 
may  be  taken  from  the  formula: 

w=(l  —  25)  cos  i, 

where  /  is  the  latitude  and  i  is  the  angle  of  inclination  of  the 
roof  with  horizontal,  both  in  degrees.  This  allowance  will 
vary  somewhat  with  the  climate.  The  pressure  of  the  wind, 
taken  as  normal  to  the  surface,  may  be  obtained  from  Duchemin's 
formula: 

/>  =  C2sine/i+sin20. 

p  —  pressure  in  pounds  per  square  foot,  0  =  angle  of  inclination 
with  horizontal,  and  C  equals  a  constant,  a  mean  value  for  which 


WOODEN  STRUCTURES  57 

is  40  Ibs.     It  will  be  noted  that  p  equals  C  for  a  vertical 
surface. 

In  computations  many  engineers  consider  the  resultant  of 
vertical  and  perpendicular  loads.  This  we  do  not  favor,  as  the 
usual  arrangement  of  the  rafters  takes  care  of  component  parallel 
to  roof.  A  very  simple  methocl  is  to  add  directly  the  entire 
weight  of  roof,  snow,  and  wind,  and  consider  them  as  acting 
perpendicularly  on  every  part  of  the  roof  surface.  To  be  sure 
this  is  higher  than  the  actual  load  on  boarding  and  rafters,  but 
it  serves  as  an  impact  allowance  and  also  to  take  care  in  a  way 
of  a  concentrated  load.  If  without  knee  braces,  the  same  method 
may  be  pursued  for  ordinary  trusses.  The  writer,  however, 
considers  the  latter  poor  engineering.  For  knee-braced  trusses, 
it  is  never  allowable.  The  proper  way  then  is  for  all  framed 
structures  to  obtain  maximum  stress  of  each  kind  after  a  full 
consideration  of  all  possible  loadings. 

Art.  29.    Computations  for  a  Roof  Truss 

Let  us  suppose  trusses  of  the  type  shown  in  Fig.  28 /  to  be 
of  40'  span,  i3/-6//  c.  to  c.,  and  angle  of  rafters  with  horizontal, 
30  degrees.  Roofing,  slate  weighing  8  Ibs.  per  square  foot. 
Material,  spruce  with  wrought  iron  rods  upset  at  ends  for  ten- 


-Upper  Chords 

I 

FIG.  29*1. — Boarding.      FIG.  296. — Rafter.  FIG.  29^. — Purlin. 

Load  Diagrams. 

sion  members.  For  the  computation  of  sheathing,  rafters,  and 
purlins,  we  will  allow  32  Ibs.  for  wind,  15  Ibs.  for  snow,  and  13 
Ibs.  for  dead  load,  making  60  Ibs.  per  square  foot,  perpendicular 
to  the  roof.  Note  that  the  actual  computation  below  shows 
the  dead  load  to  be  15.5  Ibs.  per  square  foot.  See  Fig.  29^  for 
finished  design. 

(i)  Allowable  distance  center  to  center  of   rafters,  Fig.  290. 


or    = 


58  ELEMENTS  OF  STRUCTURAL  DESIGN 

Let  us  try  J"  boards.  Then,  taking  a  strip  12"  wide,  h  =  %ff, 
b  =  i2f',  w  =  $  Ibs.  per  linear  inch,  S/=  7  50  Ibs.  per  square  inch, 
hence  1  =  42.9".  To  prevent  excessive  deflection,  this  distance 
must  be  reduced.  f"X3o  =  26.2,  we  will  make  it  6  rafters  to  a 
bay  equals  27"  spacing. 

(2)  Size  of  rafter     (Fig.  296).     Make  2"  wide. 


or       = 
Span  =  7  =  240  sec.  30  deg./3=92.4//. 

^  =  60X277(12X12)  =  11.25  Ibs.  per  linear  inch. 
5/=75o  Ibs.  per  square  inch. 


Substituting,  11  =  6.93",  and  we  will  use  2"X8",  the  next 
size  above. 

(3)  Size  of  purlin  (Fig.  290).     Carpenter  usually  arranges 


M 

FIG.  2c  d- 


rafters  to  suit  himself.  Most  unfavorable  case  is  shown  in  the 
figure.  Its  maximum  effect  is  the  same  as  that  of  a  uniformly 
distributed  load  of  equal  amount. 


or 


1  =  162",  ,5>  =  75o  Ibs.  per  square  inch. 

w  =  92.4X607(12X1  2)  =38.5  Ibs.  per  linear  inch. 
Hence, 

bh2  =  1010.     Use  10"  X  10",  bh2  =  1000. 

(4)  Size    of    members.     Estimated    weight    of    roofing    is: 
slate  8  Ibs.,  sheathing  2.5  Ibs.,  rafters  2  Ibs.,  purlins  3  Ibs.;  total 


WOODEN  STRUCTURES 


59 


15.5  Ibs.  per  inclined  square  foot.  Estimated  dead  weight  of 
truss  is  J  13.5X40(1+0.15X40)=  1890$.  Dead  panel  load 

=  — —+15. 5X  13.5  X  7.7=  1920$.     Panel  load  for   snow  =  15 
6 

X 1 3.5X40/6  =  1350$.  Wind  per  inclined  square  foot  is  40X2 
sin  30  deg./i+sin2  30  deg.=  32$.  Wind  apex  load=  32  X  7.7 
X  13.5  =3340$.  Consider  truss  as  fixed  at  both  ends. 


Total  Stresses  in  Kips. 

In  Inches. 

Mem- 
ber. 

Dead 

Snow 

Wind 
L. 

Wind 
R. 

Max. 

Allow. 
Unit 

Area 
Re- 

Use. 

Area 
Fur- 

Ex- 

Remarks. 

Stress. 

quir'd 

nish  *d 

C 

C 

C 

C 

C 

AD 

9.60 

6.75 

8.70 

5-74 

25-05 

530 

47.2 

8"X  8" 

64.0 

16.8 

Z=92" 

C 

C 

C 

C 

C 

BF 

7.68 

5-40 

6.79 

5-74 

19.87 

530 

37-4 

8"X  8" 

64.0 

26.6 

Same  as  AD 

C 

C 

C 

C 

C 

CH 

5.76 

4-05 

4-85 

5-74 

15.55 

530 

29.4 

8"X  8" 

64.0 

34-6 

" 

T 

T 

T 

T 

T 

DM 

8.30 

5-84 

IO.OO 

3-34 

24.14 

600 

40.2 

8"Xio" 

80.0 

39.8 

50%  for  joints 

T 

T 

T 

T 

T 

EM 

8.30 

5-84 

IO.OO 

3-34 

24.14 

600 

40.2 

8"Xio" 

80.0 

39-8 

•  ' 

T 

T 

T 

T 

T 

CM 

6.64 

4.66 

6.67 

3-34 

17.97 

600 

30.0 

8"Xio" 

80.0 

50.0 

Same  as  DM 

C 

C 

C 

C 

EF 

1.92 

1.35 

3.82 

0 

7-09 

462 

15-3 

4"X  6" 

24.0 

8.7 

1=92" 

C 

C 

C 

C 

GH 

2,56 

i.  80 

5.07 

0 

9-43 

478 

19-7 

6"X  6" 

36.0 

16.3 

1=122" 

DE 

o 

o 

0 

0 

0 

12000 

0.0 

i  rd.  |" 

0.31 

0.31 

Minimum  size 

T 

T 

T 

T 

FG 

0.96 

0.68 

0 

12000 

0.30 

i  rd.  f" 

0.31 

O.OI 

Upset  at  ends 

T 

T 

T 

T 

T 

HE' 

3-84 

2.70 

3-83 

3-83 

10.37 

I2OOO 

0.87 

2  rd*.  |" 

0.88 

O.OI 

1  • 

\ 

(5)  Joint  ADM .  Make  like  Fig.  262.  Bearing  area  required 
for  the  stress  in  DM  is  25.05  cos  3o°/iooo  =  2i.7  sq.in.  Use 
two  notches,  each  8"  wide  by  if"  deep,  affording  22.0  sq.in. 
bearing  area.  Shearing  length  required  is,  25.05  cos  3o°/8X8o 
=  34.0".  Make  two  of  i'-6"  as  shown  in  Fig.  2Q/.  For  stress 
in  AD,  25.05  cos30°/77o  =  28.2  sq.in.  Use  3i"x8"  bearing. 
Allowing  3000  Ibs.  per  sq.in.  shear,  necessary  thickness  of 
casting  is,  25.05  cos  3o°/3oooX8  =  0.91 ".  Using  an  allowable 
flexural  stress  of  5000  Ibs.  per  sq.in., 


Here,  TF  =  25.05  cos  30°  =  2 1,700  Ibs.,  /  =  3-5",  b  =  &",  6*7=5000 
Ibs.  per  sq.in.     Substituting,  2  =  2.39".     In   Fig.  2o/,  casting  is 


60 


ELEMENTS  OF  STRUCTURAL  DESIGN 


made  ij"  thick.  Since  required  thickness  varies  as  distance 
from  the  top,  the  lower  half  would  be  deficient  in  strength. 
The  filleting  of  the  corners  of  the  casting,  Art.  16,  would  help 
some  by  increasing  strength  of  iron  and  lowering  point  of 
application  of  resultant  pressure.  Also  stiffening  ribs  might  be 
employed.  In  any  event,  supplement  design  as  shown  with  a 


special  detail  of  the  casting,  giving  necessary  dimensions  at 
important  points. 

(6)  Area  washers. 

For  DE  and  FG,    3550/300  =  11.8  sq.in.,  use  4"  O.  G.  Washer. 
For  HE',  10370/300  =  34.6      "     "    4.5"X8"  Washer, 

special. 

(7)  Notches  for  EF  and  GH.     (Fig.  290.) 


Total 
Pressure 
in  Kips. 

Area 
.      Sq.  in. 

Pressure 
in  Lbs.  per 
Sq.  In. 

Inclin. 
with  Grain. 
Degrees. 

Allowable 
Pressure.    Lbs. 
per  Sq.  In. 

pl 

7.40 

49-8 

148 

74 

430 

P2 

8.20 

13-5 

610 

49 

620 

Pz 

9.80 

38.4 

255 

72 

440 

Pi 

4.80 

12.  O 

400 

79 

390 

Pi 

3-60 

48.7 

75 

79 

390 

A 

6.90 

9.0 

770 

30 

770 

P-, 

6.80 

30.0 

230 

66 

49° 

PS 

6.  20 

12.0 

5io 

60 

530 

WOODEN  STRUCTURES 


61 


i 


:?  ^"^       7> 

if  5§ 
i| 


FIG.  2Q/. 


62  ELEMENTS  OF  STRUCTURAL  DESIGN 

(8)  Splice  at  center.  Use  J"  steel  bolts  and  two  fish  plates, 
each  3"Xio".  Value  of  bolts,  Art.  26,  is  2000  Ibs.  each. 
Number  required  is  17,970/2000  =  9. 

Art.  30.    Trussed  Beams  * 

Figs.  300  and  c  show  the  styles  known  as  the  king  and 
queen  post  truss  respectively.  They  are  trussed  beams  only 
when  horizontal  chord  is  continuous.  Computations  often 
assume  them  to  be  jointed  structures.  Where 

ICY  i/v 

C 


<0'    ••  '^— i        the  angle  of  inclination,  6,  is   20°  or  more,  with 


- — M     horizontal,  the  error  will  not  be  a  serious  one. 


FIG.  3oa.— King     We  sometimes  find  them  inverted,  but  the  depth 
Post  Truss.        is  then  made  such  that  they  need  not  be  con- 
sidered  as   trussed  beams.     Taking   the    usual 
case  of  constant  sections  and  uniform  load,  the  correct  method 
for  either  of  the  above  trusses  is  as  follows: 

(1)  Assume    a    jointed    structure    and    determine    sections. 
This  assumption  is  for  the  purpose  of  obtaining  sizes  and  is 
carried  no  farther. 

(2)  Compute  the  deflection  at  panel  points  caused  by  any 
uniform  load,  Wi,  acting  on  entire  length  of  top  chord,  con- 
sidered  as   a   simple   truss.     Reactions  must  be   obtained  by 
treating  beam  as  continuous. 

(3)  Compute  the  uniform  load,  W2,  which  will  cause  equal 
deflections  at  panel  points  when  the  top  chord  is  considered 
a  simple  beam  for  its  entire  span. 

(4)  Then,    for   any   uniform   load,    W2/(Wi+W2)    of   that 
load  acts  as  if  on  a  simple  beam  of  length  equal  to  the  span. 
J^i/(J^i+J^2)   of  that  load  acts  as  in  a  continuous  beam.f 
From  the  reactions  for  the  same,  stresses  for  the  truss  may  be 
determined. 

(5)  Those  in  the  beam  are  then  the  result  of  compression 
due  to  truss  action,  plus  bending  due  to  W2  X Load/ (Wi-\- W2) 

*  See  "Modern  Framed  Structures,"  by  Johnson,  Bryan,  and  Turneaure, 
Part  II,  p.  408.  While  theory  given  here  bears  a  strong  resemblance  to  that 
in  above  reference,  it  was  consulted  only  after  manuscript  was  finished. 

t  This  follows  from  the  fact  that  deflections  due  to  truss  action  and  that  due 
o  beam  action  must  be  the  same  at  panel  points. 


WOODEN  STRUCTUKES 


63 


on  simple  beam  of  span  length,  plus  bending  due  to  Wi  XLoad/ 
O^i+W^)  on  a  continuous  beam  with  supports  at  each  panel 
point  of  the  truss.  * 

(6)  If  stresses  so  found  are  close  to  allowable  values,  details 
may  be  determined  for  the  final  design;  otherwise,  revise  and 
recompute. 

As  an  example,  let  us  take  a  beam  whose  span  is  20  feet 
with  a  depth  at  center  of  2  feet  as  shown  in  outline  in  Fig. 
300  and  as  detailed  in  Fig.  306.  Let  the  load  be  2000  Ibs.  per 
lineal  foot. 

(1)  Assuming    discontinuity    in   top    chord,   stresses    are; 
be,  20,000  #C;    ab,  50,000  ^C;    ac,  51,000^7;    bending  in  ab, 
20,000X120/8  =  300,000    in. Ibs.     Use   yellow   pine.     Allowable 
compression,   1200— i5//d;    flexural  stress,   1500;    bearing  600 
and    1500;    E,    1,600,000.     For   iron,    10,000   in   tension   and 
E  =  2 5, 000,000,  all  in  pounds  and  inches. 

For  be  we  will  try  a  4"Xi2",  larger  than  necessary  but 
affording  a  good  design.  If  we  take  the  top  chord  as  made 
of  two  timbers,  each  8"  wide  by  10"  deep,  its  stresses  will  be 

50,000/160+6X300,000/16X10X10    =1437  Ibs.  per  sq.in. 
Required  area  of  rod  =  5 1,000/10,000  =  5.1  sq.in. 
Use  one  round,  2  9/16"  dia.,  area  =  5.i6  sq.in. 

(2)  Deflection  due   to  a  uniform  load  of  1000  Ibs.     Load 
on  truss,  625  Ibs.     Everything  in  pounds  and  inches. 


Member. 

s 

Stress. 

I 

Length. 

A 
Area. 

E 
Mod.  Elas. 

sniAE 

ab 
be 

1562 
625 

240 
•            24 

1  60 
48 

1,600,000 
1,600,000 

2.29 

O.I2 

ac 

1593 

245 

5-16 

25,000,000 

4.83 

Total  

7   24 

Deflection  equals  7<24/625=o.oii6/ 


64  ELEMENTS  OF  STRUCTURAL  DESIGN 


f  \  -n  fl    *•  A 

(3)  Deflection  =  0.01  io=——  --  —  -. 

384  X  i  ,600,000  X  1  6  X  io3 
Hence  P^2  =  137  pounds. 

(4)  Of  this  uniform  load  of  2000  pounds  per  lin.  ft.,  137/1137 
equals    240   Ibs.,    acts  as   on  a  simple   beam,  while   1760  Ibs. 
affects  truss.    Stresses  in  the  latter  are: 


ab  =  55,000  #C,        bc  =  22,000  #C,        ac  =  56,100  #7\ 
Unit  stress  in  be  equals  22,000/48    =      460  Ibs.  per  sq.in.  C. 
"       "       ac      "      56,100/5.16  =  10,900      "     "     "     T. 

(5)  Max.  moment  in  a&  occurs  where  the  shear  equals  zero. 
This  happens  at  center  and  also  at  7^/^  =  9000/2000  =  4.5  feet 
from  either  support. 

For  the  former,  M  =  9000  X  io  —  20,000  X  5      =  —  10,000  ft.  Ibs. 
For  the  latter,    .&f  =  9000X4.5  —  9,000X2.25  =  20,250  ft.lbs. 
Stress  in  db=  —  55,000/160=4=6  X2o,25oXi2/(i6XioXio) 

—  344=1=911  =  I255C  or  5677  in  Ibs.  per  sq.in. 

(6)  The  stress  in  ac  is  greater  than  that  allowable.     As  we 
make  this  member  larger,  still  more  of  the  load  will  come  on 
the  truss.     About  a  2  11/16"  rod  is  required,  we  will  make  it 
2j"  diameter  and  recompute.     For  the  deflection  in  (2),  we  get 
.0106".     The  uniform  loads  on  beam  and  truss  are  220  and 
1780  Ibs.  respectively,  and  total  stresses  are,  — 


<*&  =  55»75o  C,        fc  =  2 
The  unit  stresses  are,  in  Ibs.  per  sq.in.,  — 

ab=   1236  C,          bc=      465  C,        ac=  95807. 
A  2  11/16"  rod  might  have  done  but  ab  and  be  have  reserve 


WOODEN  STRUCTURES 


65 


strength  and  it  is  best  to  have  a  little  in  ac.  It  would  not  be 
advisable  to  stress  ab  the  full  allowable  flexural  value  of  1500  Ibs., 
as  it  is  in  part  a  compression  member.  Use  casting  at  c  designed 
for  a  load  of  22,300  Ibs  ,  concentrated  below,  and  uniformly 
distributed  over  12"  above.  Bearing  values  must  be  tested 
at  shoulders  on  be  and  for  rods  at  a. 

Problems  of  this  kind  may  often  be  advantageously  solved 
by  the  aid  of  the  method  of  least  work,  This  principle,  with 
which  the  student  should  already  be  familiar,  states  in  brief 
that  the  load  is  so  divided  among  statically  indeterminate 


a"  z'o" 


FIG.  306. — Design  of  King  Post  Truss  Shown  in  Fig.  300. 


systems  as  to  make  the  sum  total  of  the  work  a  minimum  > 
Let  us  then  apply  it  to  this  case. 

Let  Ei,  E2,  EZ,  be  moduli  of  elasticity  for  ab,  be,  and  ac  resp. 
A i,  A2,  As,  be  areas  for  ab,  be,  and  ac  resp. 
Li,  L2,  Lz,   represent  spans  ab,  be,  and  ac  resp. 
/i  be  the  moment  of  inertia  of  ab  about  an 

horizontal    axis    through    the    center    of 

gravity. 

P  be  the  load  on  the  truss. 

W  =  2wLi  =  total  load. 
0  =  tan~1  bc/ab. 

Further,  let  M  equal  the  bending  moment  in  beam  at  a 
point  distant  x  from  either  reaction,  and  let  K  represent  the 
work  done.  Then 


66  ELEMENTS  OF  STRUCTURAL  DESIGN 

where  5  designates  the  total  stress  in  bars.     Now  substituting 

W— P 

for  S,  the  stresses  in  the  different  bars,  and  for  M,  —    — x  — 


A  —  — ,  r  I  ,.       ~\~  o         '        o        ' 

Eili\    12  6  12  8  8  20 

£  P2Zi  tan  6     P2Zg  /esc2  6  sec  6     cot2  6 
2       .^4  2^2  4     \     AsEs 

Following  the  rules  of  calculus,  we  differentiate  this  expression 
with  regard  to  P  and  place  it  equal  to  zero  to  get  the  minimum 
value  of  K,  and  obtain 

p  = 5WLJ 

Q_,  .  (  Li2       tan  6     esc2  0  sec  0      cot2  0  V 
4&c,i7 1 1  H — -   —     I — — H — - — — —  I 

\U£Lll  l       ^12-^2  2^13^3  2A\£Ll  / 


Substituting  values  given  in  problem  above,  we  compute  P 
to  be  22,200  Ibs.,  in  substantial  agreement  with  the  method 
of  deflections. 

By  putting  an  initial  camber,  that  is,  an  upward  curvature 
in  the  stringer,  its  stresses  may  be  changed  a  considerable 
amount.  The  deflection  in  the  problem  just  considered  is 
0.0106X40,000/1 125*  =  .38",  about  I".  If  now  the  nuts  at 
the  end  be  screwed  up  before  the  load  is  put  on  so  that  it  has 
a  camber  of  0.38  X  2000/1 780  =  7/16",  the  load  acting  as  a 
simple  beam  will  be  zero. 

Any  load  for  the  king  post  truss  or  a  symmetrical  load  for 
the  queen  post  truss  may  be  similarly  treated.  For  the  latter 
under  unsymmetrical  loads,  above  analysis  will  not  hold,  since 
horizontal  component  of  stress  in  bottom  chords  must  be  con- 
stant. We  proceed  as  follows: 

(i)  Assume  jointed  structure  with  a  diagonal,  ce,  compute 
stresses  and  determine  sections  making 

ab  =  bc  =  cd,     ae  =  ef=fd,     and    be  =  cf. 

*  Recomputed  value  for  1137  in  (4). 


WOODEN  STRUCTURES 


67 


This  assumption  is  for  the  purpose  of  obtaining  sizes  and  is 
carried  no  farther. 

(2)  Taking  ad  as  a  simple  beam,  compute  deflections  at 
b  and  c  caused  by  given  unsymmetrical  loads,  and  call  the 
mean  of  these,  D\. 

(3)  Still  considering  ad  as  a  simple  beam,  compute  upward 
deflection,  d2,  at  either  b  or  c  due  to 

two  equal  loads,  P,  at  b  and  c.  ^ 

(4)  Taking  Fig.  30^  as    a    truss, 

find  downward  deflection,  d3,  due  to    FIG>  30c.— Queen  Post  Truss, 
the  loads  P  at  b  and  c. 

(5)  Note  that  the  truss  offers  no  resistance  to  an  upward 
movement  at  b,  accompanied  by  an  equal  downward  movement 
at  c.    Also  that  the  average  deflection  at  panel  points,  DI, 
due  to  whole  load  acting  on  beam  of  entire  span,  minus  upward 
deflection,  D2,  of  beam  due  to  reactions,  T,  carried  by  truss, 
equals  downward  deflection,  Z>3,  at  same  points  due  to  the  truss 
action.     That  is,  Di—D2=D3.     But,  because  of  the  propor- 
tionality   of    deflections,    D2  =  Td2/P    and    D3  =  Td3/P.     Sub- 
stituting, T  =  PDi/(d2+d3). 

(6)  The  stresses  in  the  truss  may  then  be  determined.     In 
the  top  chord,  besides  its  direct  compression,  it  will  be  a  simple 
beam  of  length  ad  subject  to  the  given  loads  plus  the  two  upward 
ones,  T,  at  b  and  c  just  obtained. 

(7)  If  stresses  are  satisfactory,  problem  is  completed;    if 
not,  revise  and  recompute. 

Art.  31.    Description  of  Bridges 


FIG.  3 1  a. 
Queen  Post  Truss. 


FIG.  316. 
Lattice  Truss. 


FIG.  3  ic. 
Howe  Truss. 


The  above  represents  the  leading  types  of  bridge  trusses: 

a,  the  queen  post  truss  mentioned  in  the  preceding  article; 

b,  the  lattice;  and  c,  the  Howe:  the  latter  is  the  best  and  most 
common  form. 


68  ELEMENTS  OF  STRUCTURAL  DESIGN 

There  are  usually  two  similar  trusses.  Between  them  are 
the  floorbeams,  generally  having  the  larger  dimension  for  their 
depth.  On  top  of  these  floorbeams  and  parallel  with  the  truss, 
are  stringers  with  a  depth  two  to  six  times  their  width.  On 
these  are  laid  the  ties  in  a  railroad  bridge  or  the  plank  in  a  high- 
way bridge. 

Greater  economy  may  be  obtained  by  the  use  of  deep 
stringers  but  16"  is  about  the  greatest  depth  that  can  be  easily 
obtained  and  its  width  must  not  be  less  than  one-sixth  the 
depth  on  account  of  the  tendency  of  narrow  beams  to  buckle. 

In  a  highway  bridge,  the  dead  floor  load  should  be  computed 
as  it  varies  a  great  deal  with  the  width.  For  railroad  single 
track  bridges,  400  Ibs.  per  lin.ft.  may  be  used  for  the  weight 
of  one  track,  and  one-fifth  the  live  load  for  the  weight  of  floor. 
The  weight  of  the  trusses  for  any  wooden  bridge  may  be  taken 
as  their  live  load  burden  times  one  three-hundredth  of  the  span 
in  feet.  Here  the  weight  is  for  the  same  number  of  trusses 
and  for  the  same  length  as  the  load.  If  we  take  live  weight 
in  pounds  on  each  lineal  foot  of  truss,  we  obtain  weight  of  truss 
in  pounds  per  lineal  foot. 

In  a  railroad  bridge,  ties  are  usually  spaced  12"  on  centers, 
are  9  to  12  feet  long,  and  6X8"  in  section  with  the  latter 
vertical.  However,  they  should  be  tested  for  their  loads. 
About  nine  inches  inside  of  each  rail  are  placed  the  guard  rails, 
both  these  and  the  main  rails  being  spiked  to  each  tie.  Approx- 
imately 20"  center  to  center  outside  of  main  rails  are  placed 
the  guard  timbers,  about  6"  vertical  by  8",  which  are  bolted 
to  every  third  tie. 

Six  stringers  commonly  support  the  latter.  Of  these,  two 
are  placed  under  each  rail  and  are  computed  to  carry  the  loads 
therefrom.  The  other  two  are  put  at  either  end  of  the  tie. 
The  stringers  rest  on  the  floorbeam,  these  in  turn  rest  on  the 
bottom  chord  or  are  hung  from  the  verticals.  When  the  floor- 
beams  are  not  placed  at  a  joint,  the  chord  must  be  designed 
to  carry  the  bending  moment  as  well  as  the  direct  stress. 

In  a  Howe  truss,  verticals  are  ordinarily  of  iron  or  steel 
and  are  upset  at  their  ends.  Special  washers  of  wood  or  iron 
are  often  necessary  to  take  the  stress  into  the  chords,  these 
washers  being  figured  to  carry  their  loads  when  uniformly  dis- 


WOODEN  STRUCTURES  69 

tributed.  The  verticals  usually  pass  through  the  block  of  oak 
or  cast  iron  on  which  the  diagonals  rest,  and  also  through 
the  bottom  chord. 

If  cast  iron  be  used  for  the  angle  block,  it  need  not  be 
finished.     The  lugs  at  the  top,  fig.  3  id,  should  have  a  hole 
for  a  bolt  to  fasten  in  the  diagonals.     Those 
at  the  bottom  should  be  figured  to  furnish 
sufficient  bearing  area  on  timber.     The  thick- 
ness of  the  cast   iron   at  this  point   should 
suffice  for  the  shear  and   moment.      Some-  FIG.  3 1</.— Angle  Block 
what   similar    castings    are   placed    at   the          Howe  Truss, 
bottom   of   the   top   chord  and   they  may 
also   be  used  as   bearing  blocks  for  the  laterals. 

These  are  best  kept  in  the  plane  of  the  chords.  X  bracing 
should  be  employed  at  the  panel  points  of  deck  bridges,  with 
knee  bracing  at  the  entrance  to  through  bridges. 

Chords  are  often  made  of  three  or  more  pieces.  They  are 
spliced  as  near  a  joint  as  possible.  If  compound,  pieces  should 
be  kept  at  least  two  inches  apart  and  occasional  wooden  fish 
plates  inserted  between  them.  Splices  should  be  arranged  to 
stagger,  that  is,  they  should  be  so  arranged  that  no  two  will 
occur  at  same  or  nearby  points.  Diagonals  are  usually  of 
two  timbers,  while  between  them  run  the  counters  of  one 
piece  each,  the  two  sets  being  tightly  bolted  together  at  their 
intersection. 

No  provision  is  made  for  the  expansion  due  to  the  change 
of  temperature. 


Art.  32.    Computations  for  a  Bridge 

(See  Figs.  32^  and  e) 

Let  it  be  required  to  design  a  through  Howe  truss  for  a 
single  track  railroad.  It  is  divided  into  eight  panels  of  i2/-o" 
each  making  a  total  of  g6'-o".  We  will  make  distance  center 
to  center  of  trusses  i6'-o",  thus  providing  the  necessary  i3'-o" 
in  the  clear.  Headroom  above  base  of  rail  should  be 
2o'-o",  hence  center  to  center  of  chords  will  be  made  24/-o//. 
The  live  loading  is  4000  Ibs.  per  lin.ft.  plus  a  concentration 


70  ELEMENTS  OF  STRUCTURAL  DESIGN 

of  8000  Ibs.  for  floor  system  only,  both  per  track.  For  wind 
load,  use  100  and  300  Ibs.  per  lin.ft.  on  top  and  bottom  chords 
respectively,  the  latter  to  be  treated  as  live.  Material,  hard 
pine  with  wrought  iron  tension  members. 

(i)  Size  of  stringers.  Using  four  floorbeams  to  a  panel 
length,  the  span  of  the  stringer  becomes  three  feet.  Allowing 
200  and  100  Ibs.  per  lin.ft.  per  rail  for  track  and  stringer 
respectively,  the  latter  is  a  beam  subjected  to  a  uniform  load 
of  6900  Ibs.  and  a  concentrated  load  of  4000  Ibs.  The  max- 


imum  shear  is  then  7450  Ibs.  and  maximum  moment  67,000 
in.lbs. 

Least  allowable  value  for  shear,  bh       =  1.5  X  7450/70     =  160 
"  li  moment,  bh2  =  6X67, ooo/iooo  =  40 2 

These  requirements  will  be  satisfied  by  using  under  each  rail 
two    8"  X 10"  with  the  latter  vertical. 

(2)  Size  of  floorbeam,  span  16',  Fig.  320. 

P  =  2300 X3  +4000  =  10,900  Ibs. 

Uniform  load,  estimated,  100X16  =  1600  Ibs. 
Maximum  shear,  11,700  Ibs.     Maximum  moment,  758,000  in.lbs. 

Required  in  shear,  bh       =1.5X11,700/70    =250. 
"      "      moment,  ^  =  6X758,000/1000  =  4548. 

Use  two  9"Xi6",  former  horizontal. 

A. 

i 


WOODEN  STRUCTURES 


71 


(3)  Loads. 


Dead  load  per  foot  per  truss  for  track  =  200  Ibs.  on  bottom  chord. 

floor  =400 
"  "  "  truss  =2000  X  96/300. 

=  640  Ibs.,  |  top,  |  bottom. 

Dead  upper  panel  load  is  0.32  X  12  =  3.8  kips. 

"  lower  "  "  0.92X12  =  11.0  " 
Live  lower  "  "  2.00X12  =  24.0  " 
Wind  upper  "  "  0.10X12=  1.2  " 

"     lower        "      "      0.30X12=  3.6    " 


(4)  Stresses.     Values  are  in  kips  and  kip  in. 
(See  figure  below.) 


Member. 

Dead. 

Live. 

Wind. 

Maximum. 

UiUz 

2<?    0  C 

42  o  C 

67  0  C 

Upper  chord  .  .  . 
Lower  chord..  . 

U2US 
U3U* 

LoLi 
LiL* 
I*L3 
LtL* 

UtL0 

U2Li 

44-4C 
55-5C 

25-9T 
44-  4T 
55-  5T 
59-2T 

57-QC 

41   4  C 

72.  oC 
90.  oC 

42.  oT 
72.  oT 
90.  oT 
96.  oT 

94.  2  C 

70.  <t  C 

2.2  C 

3-5C 

12.  6T* 
19.  3  T* 
23-  3  T* 
24.  6  T* 

9.1  C 

n8.6C 
149.  oC 

80.  5T 
135-  7T 
I68.8T 
179-  8T 

i6i.2C 
in  9  C 

Diagonals  

U3Lt 

24  8  C 

so  ^  C 

7tr    i  C 

U*L3 

8  3  C 

a  6  C 

41    O  C 

U\L2 

41   4  T 

3  4C 

Counters 

U2L3 

24   8  T 

10  -  C 

U3L4 

8  ^T 

2O    2  C 

II    Q  C 

UiLi 

48  o  T 

84  o  T 

132  o  T 

UzL* 

11    2  T 

63  oT 

96  2  T 

Verticals  

U3L3 

i8.4T 

4">.oT 

63.  4  T 

U*Lt 

ii.  oT 

^?o.oT 

41  oT 

*  Three  kips  is  due  to  the  effect  of  the  wind  on  the  upper  chord. 


72  ELEMENTS  OF  STRUCTURAL  DESIGN 

Stresses  in  portal.     See  Fig.  320. 

In  a,  2.1X13.4X1.414/5  =  8.0  T  or  C. 
Max.  moment  in  UiLo  is  3.5X5.0X12  =  210. 
"  UiUi  or  LoLo  is  2.1X60  =  126. 

bottom  chord.     See  Fig.  326.* 
18.5X54-8.0X36  =  711. 


FIG.  326. — Bottom  Chord. 
1.2.  Ui Ui  3.0  3.5 


d 

id 
« 

C 

n 

/a.                 cK 

4  5.0,     6.O  ,     5.O 

Uo 

,              Ife.O 

U 

\^.                  a/ 

El 

1 

7-0                    *      ID 

fe.i              J5.6 

2.1 

Loads       Moment* 


Loads 


Moments 


FIG.  32^ — Portal. 


FIG.  32^. — Diagram  Howe  Truss. 

*Two  kips  has  been  added  here  to  cover  weight  of  bottom  chord  and 
extras  and  to  allow  of  possible  misplacement  of  floorbeams  from  assumed 
position. 


WOODEN  STRUCTURES 
(5)  Table  of  unit  stresses. 


73 


Member. 

Max. 
Kips. 

Try1 
Hor.  Vert. 

Unit  Stresses 
in  Lbs.  per  Sq.  in. 

Unsup- 
ported 
Length. 
Inches. 

Allow- 
able. 

Direct. 

Second- 
ary. 

Total. 

UJJ* 

67.  gC 

I2"XIO" 

566 

566 

144 

656 

U2U3 

n8.6C 

20//XlO// 

593 

593 

144 

656 

U3U* 

149.  oC 

24//XlO// 

621 

621 

144 

656 

L*U 

80.  5  T 

3o"Xi6" 

168 

556 

724 

800 

UL, 

135-  7T 

34"Xi6" 

250 

490 

740 

800 

LzL3 

I68.8T 

38"Xi6" 

277 

440 

717* 

800 

I*Lt 

179.  8T 

38"Xi6" 

297 

440 

737 

800 

UtLo 

i6i.2C 

26"Xl  2" 

5i6 

155 

671 

161 

666 

UtLi 

iii.9C 

Twoio^Xio" 

S6o 

560 

161 

639 

U3Lz 

75-iC 

"      8"X  8" 

586 

586 

161 

600 

U<L3 

41.  9C 

"      6"X  8" 

436 

... 

436 

161 

530 

UiLt 

One    6"X  8" 

161 

530 

U2L3 

.... 

"      6"X  8" 

. 

161 

530 

U^t 

ii.  9C 

"      6"X  8" 

248 

... 

248 

161 

530 

UiL, 

132.  oT 

Two  $\"  rounds 

6860 

6860 

7000 

U2L, 

96.  2  T 

"    3"        " 

6800 

.  .  . 

6800 

7000 

U3L3 

63.  4  T 

"      2$"         " 

6450 

.  .  . 

6450 

7000 

U*L4 

41.  oT 

"     2" 

6530 

6530 

... 

7000 

Top  diags.  . 

3-8C 

One    6"X  6" 

no 

no 

1  20 

600 

Top  ties  

i.8T 

"      f"  round 

4100 

4100 

7000 

UiUi 

6.7T 

One    8"Xi2" 

70 

660 

730 

.  . 

800 

a,  Fig.  32C  | 

S.oTl 
S.oCJ 

"      4"X  6" 

333 
333 

333 
333 

84 

800 
590 

Bott.  diags. 

IS-8C 

"      6/rX  6" 

440 

.  .  . 

440 

120 

600 

I*Li 

9-4T 

One  if"  round 

6350 

6350 

7000 

UI* 

6.7T 

"    it"      " 

6770 

6770 

7000 

L3L3 

4-ST 

«      j//      « 

5720 

5720 

.  .  . 

7000 

UU 

2.7T 

«          3//          (( 

4 

6140 

6140 

7000 

L0L« 

ii.  oT 

<f      8"Xi2" 

no 

660 

770 

800 

In  the  design,  Fig.  320,  the  bridge  must  be  built  to  conform 
to  the  above  results.  The  stress  in  wooden  tension  members 
is  kept  low  to  allow  for  the  joints.  In  computing  UiLo  for 


74 


ELEMENTS  OF  STRUCTURAL  DESIGN 


FIG.  326. 


WOODEN  STRUCTURES 


75 


moment,  it  is  considered  as  a  solid  beam,  a  little  different  from 
its  actual  construction  but  probably  agreeing  closely  with  its 
strength.  It  is  better  to  nail  diagonal  batten  plates  of  say  one 
inch  stuff  along  top  and  bottom,  leaving  small  spaces  between 
for  ventilation.  For  LoLo  the  floorbeams  are  used  as  they 
will  be  amply  strong.  Bolts  and  other  details  are  not  shown 
in  the  drawing.  At  all  joints,  packing  blocks  should  be  used 
and  pieces  thoroughly  bolted  together.  In  built  up  compres- 
sion members,  care  should  be  used  that  the  slenderaess  ratio 
for  individual  members  does  not  exceed  that  for  the  column 
as  a  whole. 


Art.  33.    Trestle  Bents.*     (Fig.  321") 

While  these  may  be  computed  and  designed  like  any  other 
structure,  they  are  usually  built  from  standard  plans  evolved 
from  experience.  Standardization  is  rendered  necessary  by 
the  need  for  keeping  in  stock  the  timber  for  renewal. 

The  ties,  rails,  and  guard  timbers  should  be  the  same  as  for 
a  Howe  truss.  Stringers  are  usually  built  of  three  timbers, 


FIG. 


FIG.  336. 


Details  at  Cap. 


each  6  to  8"  wide  and  14  to  18"  deep.  They  are  well  bolted 
together  and  packed  by  fish  plates  at  caps  and  spools  (cast- 
ir^n  washers),  elsewhere  to  keep  them  2"  apart.  The  span 
varies  from  12  to  16  feet.  Separate  timbers  may  extend  over 
one  or  two  spans,  in  the  latter  case  breaking  joints.  They  may 
rest  directly  on  top  of  the  cap  of  the  bents  as  shown  in  Fig. 
330,  in  which  case  they  are  drift  bolted  to  it.  Or  "  corbels  " 
may  be  placed  underneath  as  seen  in  Fig.  336,  when  it  is 

*See  "Theory  and  Practice  of  Modern  Framed  Structures,"  by  Johnson, 
Bryan,  and  Turneaure,  1904  ed.,  Chap.  XXV. 


76 


ELEMENTS   OF  STRUCTURAL  DESIGN 


bolted  to  stringers  and  drift  bolted  to  the  cap.  Corbels  add 
to  the  cost,  contribute  to  shrinkage  and  decay,  and  should  be 
avoided. 

The  structure  which  supports  the  stringers  is  called  a  "  bent." 
These  are  usually  built  about  as  represented  in  Fig.  33^.  The 
posts  are  under  or  nearly  under  the  rail,  while  the  battered 
posts  are  placed  just  outside  at  the  top.  The  inclination  of 
the  latter  is  2  to  3"  per  foot.  Sometimes  a  square  bent  is 
used,  but  it  is  suitable  only  for  tangents  and  small  heights, 
Fig.  33^- 

The  cap  may  be  made  whole  as  shown  in  Fig.  33 a  and  b. 
In  this  case,  it  is  usually  about  i2//Xi2//Xio/  to  14'.  Or 
the  posts  can  be  mortised  into  the  cap  as  seen  in  Fig.  330.  In 


FIG.  33C. 
Typical  Bent. 


FIG.  33d. 
Square  Bent. 


FIG.  336. 

Post  Mortised 

into  Cap. 


the  latter  event,  two  6//Xi2//  are  firmly  bolted  to  the  posts, 
which  are  notched  to  receive  them.  These  posts  are  usually 
i2//Xi2//  mortised  or  doweled  into  the  sill,  also  a  i2//Xi2// 
extending  2  or  3  feet  outside  of  the  joint.  The  sills  rest  on  pile 
or  masonry  foundations,  preferably  being  firmly  bolted  thereto. 
The  bracing  in  the  plane  of  the  bent  is  called  "  sway  bracing  " 
and  may  be  omitted  if  batter  posts  are  used  and  if  the  height 
of  the  bent  does  nor  exceed  20  feet.  Each  diagonal  should  be 
2  or  3//Xi2//,  firmly  bolted  at  each  end,  and  spiked  at  each  of 
the  other  posts.  Cross  girts,  horizontal  transverse  members, 
may  be  in  pairs  bolted  to  the  posts;  or  single  members,  framed 
in  between  and  toenailed  to  them.  Sometimes  the  bents  are 
made  in  stories,  the  cross  girt  forming  the  sill  for  one  story 
and  a  cap  for  the  one  below  it. 


WOODEN  STRUCTURES 


77 


FIG.  33/. 


78  ELEMENTS  OF  STRUCTURAL  DESIGN 

The  bracing  in  a  plane  parallel  to  the  track  is  called  the 
longitudinal  bracing.  Diagonals  are  about  6"X8"  and  girts 
about  6//Xi2//.  It  is  placed  in  the  plane  of  the  center  of  track. 
Plank  bracing  in  plane  of  vertical  or  battered  posts  is  frequently 
used  and  should  be  just  as  good  if  an  efficient  connection 
between  cap  and  post  is  obtained. 

Usual  size  of  drift  or  other  bolts  is  I"  diameter. 

Except  when  using  standard  plans,  the  safety  of  which  in 
similar  locations  has  been  proven  in  practice,  loads  should  be 
estimated  and  every  piece  and  joint  carefully  proportioned 
not  to  exceed  allowable  limits.  In  designing  the  longitudinal 
bracing,  stresses  due  to  the  braking  of  the  train  must  not  be 
forgotten.  This  may  be  estimated  at  one-fifth  the  total  live 
weight.  The  sway  bracing  has  to  carry  the  wind  load,  a  high 
value  of  which  should  be  chosen  to  provide  strength  to  resist 
the  buckling  of  the  posts. 


CHAPTER  IV 

FABRICATION  OF  STRUCTURAL  STEEL* 
Art.  34.     Organization  of  Administration 

WE  pass  now  to  the  design  of  structures  largely  of  steel. 
Let  us  first  take  up  the  company,  its  men,  machines,  and 
methods  by  which  the  rolled  shapes  are  fabricated  into  bridges 
and  buildings. 

The  company  may  be  divided  into  the  following  departments: 

Executive,  Ordering,  Shipping, 

Sales,  Operating,  Erecting, 

Engineering,  Inspecting,  Financial. 

In  the  executive  department  are  the  president,  vice-president, 
general  manager,  purchaser,  and  treasurer.  They  decide  upon 
the  policy  of  the  company,  appoint  minor  officers,  and  exercise 
a  general  supervision  of  all  employees.  Those  who  occupy 
these  positions  should  have  capacity  for  handling  men  and  good 
business  judgment  in  addition  to  a  technical  education  and  a 
thorough  knowledge  of  the  work.  However,  they  are  not 
directly  productive  and  we  shall  not  consider  them  further. 

The  sales  department  endeavors  to  secure  business  for  the 
company,  that  is,  to  obtain  contracts  for  making  bridges  and 
buildings.  In  competition  they  submit  figures  based  on  esti- 
mated weights  and  drawings  obtained  in  the  engineering  depart- 
ment. See  Arts.  51,  53,  and  57.  If  the  salesmen  "  land  "  the 
job,  the  engineering  department  also  makes  the  preliminary 
order,  Art.  63,  the  detail  drawings,  Arts.  58  and  62,  and  the 
final  lists  of  materials,  Arts.  63,  64,  and  65. 

The  order  department  relists  material  and  procures  it  from 
the  mill.  Operating  department  (the  shop),  cuts,  punches, 

*See  "Roofs  and  Bridges,"  by  Merriman  and  Jacoby,  Part  III,  Chap..  IV. 
See  Eng.  Record,  Vol.  XLVTII,  pp.  360  et  seq.,  pp.  620  et  seq. 

79 


80  ELEMENTS   OF  STRUCTURAL  DESIGN 

rivets,  and  paints,  thus  transforming  this  material  into  beams, 
ties,  and  struts.  Inspection  department  examines  them  to  be 
sure  of  their  accord  with  drawings  and  specifications.  When 
passed,  shipping  department  weighs  them,  then  loads  on  cars 
which  take  pieces  to  their  destination.  Here  erection  depart- 
ment put  them  into  final  position.  Financial  department  col- 
lects the  contract  price,  pays  the  men,  and  subdivides  cost. 

Art.  35.    Plant  in  General 

The  site  of  a  plant  should  be  approximately  level  and  must 
have  ample  shipping  facilities.  Freight  charges  on  raw  material 
from  mills  to  plant  plus  that  on  finished  material  from  plant  to 
site  is  to  be  kept  as  low  as  possible.  Abundance  and  cheap- 
ness of  labor  are  important. 

The  framework  of  the  building  is  usually  steel.  Any  standard 
roofing  or  siding  may  be  employed.  For  the  latter,  brick  or 
concrete  is  preferred,  but  they  are  expensive  and  hard  to  alter. 

The  grouping  of  the  buildings  should  be  such  as  to  reduce 
cost  of  handling  to  a  minimum.  It  is  usual  to  so  arrange 
the  yard  that  raw  material  begins  at  one  end  and  gradually 
works  through  to  the  other,  coming  out  as  th'e  finished  product. 
This  keeps  length  of  haul  down  to  a  minimum.  To  economize 
on  cost,  systems  of  narrow  gage  yard  tracks  should  be  installed, 
see  Fig.  35.  In  connection  with  these,  there  are  numerous 
bridge  and  jib  cranes,  Fig.  36.  Together  the  track  system 
and  the  cranes  do  all  of  the  heavy  moving  and  a  great  deal 
of  the  lighter. 

Raw  material  is  unloaded  by  cranes  from  cars  on  the  siding 
to  stock  yard,  Art.  36.  When  shop  is  ready  for  fabrication, 
the  cranes  load  it  on  the  push  cars  whence  it  is  taken  through 
the  shop.  At  each  place  where  work  is  to  be  done,  it  is  lifted 
off  cars  and  afterwards  replaced.  Another  crane  at  the  other 
end  of  the  works,  loads  on  cars  for  shipment. 

The  principal  buildings  are : 

Offices,  Main  Shop,  Forge  Shop, 

Power  Plant,  Machine  Shop,  Foundry. 

Templet  and  Pattern  Shop, 


FABRICATION  OF  STRUCTURAL  STEEL 


81 


82  ELEMENTS  OF  STRUCTURAL  DESIGN 

The  offices  are  preferably  located  at  entrance,  near  enough 
to  the  works  to  be  convenient,  yet  far  enough  away  to  escape 
the  smoke  and  noise.  A  large  part  of  this  building,  usually 
the  upper  floors,  will  be  devoted  to  drawing  rooms.  These 
should  be  light  and  well  ventilated.  Space  must  be  provided, 
not  only  for  the  regular  estimating  and  detailing  forces,  but 
also  for  the  erecting  and  operating  departments.  The  former 
designs  tools  and  appliances  for  erection  work,  Art.  49.  The 
latter  performs  a  similar  office  for  the  equipment  of  the 
shop. 

In  the  power  house  are  located  the  necessary  boilers  and 
engines.  The  steam  which  the  former  produces  may  be  used: 

(a)  Directly. 

(i)  To  warm  buildings.     (2)  Power.      (3)  Water  supply. 

(b)  Or  converted  into: 

(1)  Electricity  for  light.  (3)  Pneumatic  pressure. 

(2)  Electricity  for  power.  (4)  Hydraulic  pressure. 

(ai)  and  (#3)  are  outside  the  scope  of  this  book.  (02)  is 
not  common.  Electric  lighting  consists  of  arc  lamps  for  general 
lighting  and  incandescent  for  the  individual  tools.  Electricity 
for  power  may  be  furnished  by  motor  to  machines  through 
direct  connection  or  line  shaft  and  belts.  Generally  speaking, 
compressed  air  is  used  for  portable  drills,  reamers,  riveters, 
chippers,  and  so  forth,  also  for  furnishing  draft,  for  sand  blast, 
and  for  painting.  Hydraulic  pressure  is  employed  in  forging, 
upsetting,  and  riveting — 80  Ibs.  per  sq.in.  for  pneumatic  and 
800  for  hydraulic  represent  average  practice.  Occasionally 
two  systems  of  different  pressures,  either  in  air  or  water  may 
be  used. 

We  shall  not  consider  the  foundry  here  as  its  principles 
have  been  taken  up  in  Art.  16. 


FABRICATION  OF  STRUCTURAL  STEEL 


83 


Art.  36.     Stock  Yard.     (Fig.  36.) 

Material  is  unloaded  by  cranes  from  railroad  cars  and 
deposited  in  the  stock  yards.  Size,  length,  and  contract  number 
are  marked  thereon  and  it  is  placed  where  it  can  be  found  when 
needed.  The  yard  may  or  may  not  be  under  cover.  Some 


FIG.  36. — Pennsylvania  Steel  Co. 

shelter  must,  however,  be  provided  for  the  machines.  These 
are  principally  straightening  rolls.  There  are  two  kinds,  one 
for  plates  and  another  for  angles.  Either  consists  of  a  number 
of  adjustable  rolls  between  which  steel  is  passed.  Other  shapes 
may  be  straightened  by  hammering.  Shears  and  cold  saws 
sometimes  occur  but  they  are  more  appropriately  described 
under  the  head  of  "  Main  Shop." 


84 


ELEMENTS  OF  STRUCTURAL  DESIGN 


FABRICATION  OF  STRUCTURAL  STEEL 


85 


Art.  37.    Main  Shop.     (Fig.  $7a  and  b.) 

Here  the  main  operations  of  fabrication  are  carried  on. 

At  the  end  nearest  the  stock  yard,  a  space  is  reserved  for 
laying  out  material,  either  on  the  steel  itself,  or  by  templet, 
Art.  40. 

Next  come  the  shears.     These  may  be 


(1)  Beam, 

(2)  Angle, 


(3)  Plate, 

(4)  Split, 


(5)  Gross. 


FlG,  376. — Main  Shop,  Pennsylvania  Steel  Co.,  Harrisburg,  Pa. 


In  shearing,  two  strong  plates  are  so  adjusted,  Fig. 
that  they  just  slip  by  one  another.  When  cut  is  made,  it  must 
begin  at  edge,  and  successively  shear  off  the  material.  The 
supports  and  means  for  handling  different  shapes  vary. 

In  the  beam  shear,  a  number  of  different  blades  are  necessary 


86 


ELEMENTS  OF  STRUCTURAL  DESIGN 


8 


in  order  to  fit  various  sizes  of  I  beams  and  channels.     It  is 

not  a  common  tool. 

An  angle  shear  is  shown  in  Fig.  3  yd.  May  be  single  or  double 
as  shown.  In  the  better  class  of  machines, 
they  are  made  to  revolve  so  that  a  skew  cut 
may  be  made  without  moving  piece  They 
should  be  powerful  enough  to  cut  an  8"  X8"  X  i" 

angle- 

Fig.  370  represents  a  plate  shear.  This  too 
may  be  fixed  or  revolving.  A  fully  equipped  shop  will  have 
one  machine  capable  of  cutting  i2o//Xi//  plate. 


riG.  37C. 
Shear  Blades. 


FIG.  37</. — Double  Angle  Shears,  Long  &  Alstatter,  Hamilton,  Ohio. 

There  are  also  small  shears  as  seen  in  Fig.  377".  The  blades 
may  be  parallel  to  the  axis  of  the  machine  (cross  shears),  or 
perpendicular  thereto  (split  shears). 

Among  the  accessories,  we  may  name  the  circular  cold 
saw  and  a  machine  for  planing  the  rough  edges  of  sheared 
plate.  Also  the  coping  machine,  Fig.  37^,  which  shears  -off  the 
flanges  of  I  beams  and  channels;  after  this  has  been  done, 


FABRICATION  OF  STRUCTURAL  STEEL 


87 


remainder  is  a  plate  and  may  be  easily  taken  off  by  an  ordinary 
shear  which  is  a  part  of  the  machine.     See  Fig.  37g'. 


Next  come 
lows: 


the  punches,  which  may  be  classified  as 


fol- 


88 


ELEMENTS  OF  STRUCTURAL  DESIGN 


FIG.  3 7/.— Shear,  Baird  Machinery  Co.,  Pittsburgh,  Pa. 


FIG.  37g— Coping  Machine,  Long  &  Alstatter  Co.,  Hamilton,  Ohio. 


FABRICATION  OF  STRUCTURAL  STEEL 


(1)  Single.     (3)  Rack  or  spacing 

(2)  Gang.  tables. 


(4)  Multiple. 

(5)  Special  devices. 


Essential  idea  of  a  punch  is  a  rod  of  steel  passing  through 


ID 


FIG.  37g'. 


FIG.  37/r. 


- 


FIG.  37*'.— Single  Punch,  Long  &  Alstatter  Co.,  Hamilton,  Ohio. 

a  hole  just  a  trifle  larger.  If  now  a  plate  be  put  between  the 
two,  the  former  forces  out  an  irregularly  shaped  piece  of  metal 
as  shown  in  Fig.  37^. 


90 


ELEMENTS  OF  STRUCTURAL  DESIGN 


(1)  is  shown  in  Fig.  372'.     Twice  the  distance  between  tool 
and  back  of  throat  is  the  width  of  the  largest  plate  it  can  punch. 

(2)  is  similar  to  (i)  except  that  there  are  several  punches 


to 

3 


instead  of  one.     It  may  be  used  for  any  standard  grouping 
of  holes. 

In  (3)  there  are   a   number  of  punches  in  a  line,  usually 
four,  with  a  device  that  enables  any  combination  to  be  used 


FABRICATION  OF  STRUCTURAL  STEEL  91 

at  one  stroke.  The  shape  which  is  being  punched  is  fed  forward 
by  a  mechanically  operated  table.  One  type  has,  at  the  side 
of  track  for  table,  numerous  pieces  of  steel.  A  lever  in  the 
side  of  table  engages  one  of  these  pieces.  When  released  by 
attendant,  it  catches  on  next  piece.  Of  course,  these  must 
be  carefully  set. 

(4),  Fig.  37;,  is  like  (3)  except  that  it  is  larger  and  has  more 


FIG.  37&.  FIG.  377. 

Punching  Washer  Fillers.  Punch  for  Lattice  Bars. 

punches.     They   sometimes   have   sufficient    width    for     120" 
plate. 

Among  the  special  devices,  we  may  mention  a  machine 
with  two  dies  of  different  diameters.  This  punches  out  material 
as  shown  in  Fig.  37^.  The  numerals  signify  the  number  of 


FIG.  3 w— Pneumatic  Drill,  Chicago  Pneumatic  Tool  Co.,  Chicago,  HI. 

the  stroke.    Another  machine  has  a  punch  as  shown  in  Fig. 
37/.     It  is  used  to  cut  out  lattice  bars  as  shown  in  Fig.  56*. 

Drills  are  used  for  boring  holes  in  metal.  Reamers  are 
fluted  tools  employed  to  enlarge  a  hole  already  formed.  Both 
may  be  used  in  the  same  machine.  There  are  four  common 
types: 

(1)  Pneumatic  drill.  (3)  Radial  drill. 

(2)  Ordinary  drill  press.  (4)  Boring  mill. 


92 


ELEMENTS  OF  STRUCTURAL  DESIGN 


(i),  Fig.  37W,  is  a  small  compressed  air  engine  or  turbine, 
turning  a  shaft  to  which  is  attached  the  tool.  It  obtains  its 
air  from  the  supply  lines  by  means  of  armored  hose. 

(2)  as  shown  in  Fig.  37^,  is  the  usual  drill  press. 


FIG.  37w. — Ordinary  Drill,  Baird 
Machinery  Co.,  Pittsburgh,  Pa. 


FIG.  370.— Radial  Drill. 


(3),  Fig.  370,  is  hardly  less  familiar.  It  consists  of  small 
drills  on  swinging  arms  so  arranged  that  they  can  move  back 
and  forth.  They  are  mounted  in  gangs  and  their  support  may 
be  movable. 

(4)  There  are  two  kinds  of  boring  mills:   the  horizontal  and 


FIG. 


FIG.  37?. 
Tools  for  Boring  Mill. 


the  vertical.  They  are  much  like  drills  and  can  be  employed 
as  such.  In  general,  they  are  used  for  large  holes.  The  tool 
for  boring  eyebars  is  shown  in  Fig.  37^.  One  like  Fig.  37^ 
will  enlarge  a  punched  hole. 


FABRICATION   OF  STRUCTURAL  STEEL  93 

Methods  of  driving  rivets  will  be  taken  up  later.    There 
are  four  types  of  machines: 

(1)  Percussion.  (3)  Pneumatic  hydraulic. 

(2)  Toggle  joint.  (4)  Hydraulic. 

A  percussion  riveter,  Fig.  377-,  is  a  piece  of  steel  forced  back 


FIG.  37r. — Pneumatic  Riveter  (without  tool),  Chicago  Pneumatic  Tool  Co., 

Chicago,  111. 

and  forth  like  a  steam  pile  driver  or  a  rock  drill.  This  impinges 
on  a  stationary  die  which  forms  the  head  of  the  rivet.  Motive 
power  is  compressed  air  from  the  company  mains. 

In  (2),  Fig.  375,  an  air  piston  works  on  a  toggle  joint,  thus 


FIG.  37$. — Toggle  Joint  Riveter,  Chicago  Pneumatic  Tool  Co., 
Chicago,  HI. 

producing  required  pressure.     Satisfactory  adjustment  is  quite 
difficult. 

(3).     Here  the  air  piston  acts  on  a  plunger  which  in  turn 
compresses  oil.     This  drives  the  piston  carrying  the  riveting  die. 


94 


ELEMENTS  OF   STRUCTURAL  DESIGN 


(4),  Fig.  37/.     This  consists  of  two  jaws,  on  each  end  of  which 
is  a  die.     One  of  these  is  attached  to  a  powerful  hydraulic  piston. 

Air  may  also  be  used  here. 

(i)  is  portable.  (4)  is 
usually  fixed,  while  (2)  and  (3) 
may  be  either.  Whether  it  is 
best  to  make  riveter  portable 
or  not  depends  upon  size  of 
piece  handled. 

Among  other  machines,  we 
may  mention  the  end  milling 
machine,  or  rotary  planer, 
Fig.  37^,  in  which  a  rotating 
wheel  carries  in  its  circum- 
ference teeth  which  remove 
metal  to  form  a  smooth  sur- 
face. Sometimes  there  are 
two  planers  so  made  that  they  can  be  put  a  fixed  distance 
apart.  Again  they  are  mounted  to  rotate  in  order  to  plane 
to  a  bevel. 


FIG.  37/. — Hydraulic  Riveter. 


FIG.  37«. — Rotary  Planer,  Niles-Bement-Pond  Co.,  NewYork. 


FIG.  37^  FIG.  37^.  FIG.  373;. 

Stiffeners.  Tool  for  Fitting.      Tool  for  Fitting 

Chipping  work  is   done  by   a  pneumatic   tool   similar   to 
riveter  except  that  a  chisel  is  substituted  for  the  die. 


FABRICATION   OF  STRUCTURAL  STEEL  95 

Another  machine  which  may  be  found  in  main  shop  is  one 
for  fitting  the  stiffeners  of  a  plate  girder  into  the  flange  angles, 
Fig.  372.  The  superfluous  metal  may  be  removed  by  a  special 
milling  machine  with  a  cutter  like  Fig.  372^,  or  a  shaper  with 
tool  like  Fig.  37^.  See  next  article  for  a  definition  of  these 
machines. 


Art.  38.    Machine  Shop 

The  functions  of  a  machine  shop  are  threefold : 
(i)  To  do  mechanical  work  on  structural  parts.  Such  are 
drilling,  boring,  planing,  turning,  and  milling.  It  will  be 
noticed  that  many  of  these  operations  occur  in  other  shops. 
This  is  because  it  saves  time  and  labor  when  handling  heavy 
pieces  to  keep  tools  near  by.  We  find  then  that  the  machine 


FIG.  38a. — Lathe,  Baird  Machinery  Co. 

shop  takes  up  this  work  only  when  members  are  light  or  there 
is  a  great  deal  to  be  done  on  them.  Among  such,  we  may 
mention  the  turning  of  pins  and  rollers,  the  threading  of  pins, 
pin-nuts  and  pilot  nuts,  the  planing  of  base  plates  and  cast- 
ings, and  so  forth. 

(2)  To  do  machine  work  where  a  part  of  a  structural  job. 
Such,  for  example,  is  the  machinery  in  turntables  and  movable 
bridges.     Another  example  is  the  making  and  repair  of  erection 
tools. 

(3)  To  manufacture  and  maintain  such  machines  and  tools 
in  the  plant  as  are  not  purchased  outside. 

The  idea  of  machine  work  is  either  to  cut  holes  or  recesses 
in  metal,  for  example,  a  slotted  hole,  Fig.  6ib,  or  a  key  seat;  or 


96 


ELEMENTS   OF   STRUCTURAL  DESIGN 


to  make  a  surface  exact.     Thus  a  roller   must   be  truly  cylin- 
drical, and  surfaces  which  slide  must  be  exact  planes. 
The  principal  machines  found  here  are : 


(1)  Drill  presses.  (3)  Lathes. 

(2)  Boring  machines.     (4)  Shap 


•ers. 


(5)  Planers. 

(6)  Milling  machines. 


(i)  and  (2)  have  already  been  explained  in  preceding  article. 

Lathes,  Fig.  380,  have  a  revolving  support  and  a  tool-holder 

which  travels  parallel  to  piece  but  is  made  adjustable  to  bring 


FIG.  386.— 24"  Crank  Shaper.    Queen  City  Machine  Tool  Co. 

tool  nearer  to  or  farther  from  work.  As  is  obvious,  .they  finish 
a  surface,  generated  by  the  revolution  of  a  straight,  broken, 
or  curved  line  about  the  axis  of  rotation.  They  may  also  be 
employed  to  make  screw  threads. 

In  shapers,  Fig.  38^,  piece  has  slow  lateral  motion,  while 
tool  in  an  adjustable  support  moves  across  the  work.  This 
will  finish  plane  and  cylindrical  surfaces  generated  by  a  straight, 
broken,  or  curved  line ;  its  principal  use  is  for  plane  surfaces. 

Planers,  Fig.  38^,  form  the  same  kind  of  surfaces  as  shapers. 
However,  the  piece  moves  instead  of  the  tool  which  has  a  slow 


FABRICATION   OF  STRUCTURAL   STEEL 


97 


FIG.  38*;. — Cincinnati  Planer  Co. 


FIG.  38^. — 42"    Planer  Type   Milling  Machine.     Niles-Bement-Pond   C<x 

New  York. 


98 


ELEMENTS  OF  STRUCTURAL  DESIGN 


lateral  motion  and  is  adjustable.  In  general,  planer  is  employed 
on  large  work. 

Milling  machine,  Fig.  38^,  is  one  for  forming  exact  surfaces 
by  means  of  revolving  tools  or  cutters. 

An  average  allowance  for  plates  is  1/16"  for  each  planing. 


o 


FIG.  38^. 


FIG.  38/. 


Plain  Rollers. 


In  ordering  hot  rolled  rounds,  add  J"  to  turned  diameter;   for 
forged,  add  \" . 

As  an  example  of  machine  work,  let  us  take  rollers  as  used 
for    large    expansion    bearings.     All    exterior    surfaces    except 


Tapped 


0 


FIG.  3* 


FIG.  3  8  A. 


Segmental  Rollers. 


ends  must  be  finished.  For  Figs.  38^  and  /,  rollers  are  sawn 
from  rounds,  and  then  turned  in  a  lathe.  Figs.  38^  and  h  may 
be  planed  and  turned  from  a  round,  from  a  rectangular  bar, 
or  from  a  forging  of  about  the  same  shape. 


Art.  39.    Forge  Shop.     (Fig.  39.) 

Here  we  make  rivets  and  bolts,  upset  eyebars,  manufacture 
miscellaneous  forgings,  and  do  general  blacksmith  work.  We 
find  in  this  shop,  rivet-  and  bolt-making  machines  into  which 
the  heated  rod  is  thrust  and  from  which  it  emerges  in  small 
pieces,  cut  to  proper  length,  and  with  one  end  upset  to  correct 
shape.  Here  are  located  machines  for  making  nuts  and  putting 
thread  on  bolts. 

Where  the  eyebars  are  made,   we  find  first  the  furnaces 


FABRICATION  OF  STRUCTURAL  STEEL 


99 


in  which  the  raw  material  is  heated,  next  the  upsetting  machine 
which  enlarges  head  to  the  final  shape.  Then  we  have  a  punch 
which,  while  the  head  is  still  hot,  trims  off  the  irregular  pro- 
jections and  punches  a  hole  one  inch  smaller  than  finished 
diameter.  There  are  also  straightening  machines  as  already  de- 
scribed and  annealing  furnaces  to  take  out  any  internal  stresses 


FIG.  39. — Partial  View  of  Forge  Shop,  American  Bridge  Co.,  Ambridge,  Pa. 

caused  by  preceding  treatment.  Near  them  is  located  a  boring 
mill,  composed  of  two  drills,  the  distance  between  which  is 
adjustable. 

For  the  production  of  miscellaneous  forgings  and  general 
blacksmith's  work,  we  find  the  usual  equipment.  Special 
mention  might  be  made  of  the  steam  hammer  and  machines  for 
bending  steel  to  a  form,  "  bulldozers." 


100  ELEMENTS  OF   STRUCTURAL  DESIGN 

Art.  40.    Templets  * 

Steel  work  consists  in  the  main  of  the  rolled  shapes,  which 
we  have  considered  in  Chap.  II,  cut  to  exact  dimensions.  For 
the  purpose  of  fastening  these  different  shapes  together,  holes 
are  placed  at  frequent  intervals.  These  cuts  and  holes,  made 
as  shown  on  drawings  furnished  by  the  engineering  department, 
are  located  in  four  ways : 

(1)  By  laying  out  on  the  steel  directly. 

(2)  By  templets. 

(3)  By  rack  or  multiple  punch.     (See  Arts.  37  and  44.) 

(4)  Special  processes. 

(i)  is  the  best  method  where  there  are  only  a  few  holes 
in  a  long  piece,  or  where  there  are  only  one  or  two  pieces.  The 
mechanic  works  directly  on  the  steel  putting  a  punch  mark 
wherever  a  hole  is  to  go  while  the  cuts  are  indicated  by  a  series 
of  such  punches;  (2)  Templets  ("template"  is  also  correct) 
are  pieces  of  wood  designed  to  be  clamped  on  the  steel  while 
the  necessary  dimensions  are  transferred  from  it.  Holes  about 
\"  diameter  are  bored  in  the  wood  opposite  those  which  are 
to  be  punched  in  the  steel.  Pasteboard  or  cast  iron  may  also 
be  used  as  a  material. 

As  an  example  of  (4),  we  may  mention  a  punch  with  a 
special  table,  carrying  a  plate  to  be  punched  and  a  pattern 
plate.  When  a  die  attached  to  machine  is  placed  in  any  hole 
in  pattern,  the  punch  is  directly  over  same  spot  in  other  plate, 
and  accordingly  clutch  may  be  thrown  in  and  hole  made  as 

usual.  Thus  this  machine  saves 
preparation  of  templet,  and  the 
work  of  laying  out. 

A  very  common  term  in  tech- 
nical work  is  right  and  left. 
FIG.  4oa.  If  about  any  plane  as  an  axis, 

Left.  Right.  we  construct  a  solid  symmetrical 

with  a   given   solid,  the   original 
is  called  "  right  "  while  the  other  is  "  left,"  Fig  400. 

Axiom  i.  The  position  of  the  axis  is  immaterial,  as  the 
resulting  left  will  be  the  same  for  all  positions. 

*Eng.  News,  Vol.LV,  p.  326. 


FABRICATION  OF  STRUCTURAL   STEEL  101 

Axiom  2.  The  left  of  a  body  containing  a  plane  of  symmetry 
is  the  same  as  its  right. 

Axiom  3.  The  left  of  a  composite  body  is  composed  of 
parts  each  of  which  is  a  left  of  the  corresponding  parts  in  the 
original. 

The  templet  for  a  small  plate  is  a  piece  of  wood  of  exactly 
the  same  area  but  not  necessarily  the  same  thickness.  That 
for  a  large  plate  is  usually  framed  together  like  a  truss  with  the 
pieces  so  placed  as  to  contain  the  holes. 

The  templet  for  an  angle  is  made  as  shown  in  Fig.  406. 
If  the  angle  be  right  and  left,  it  is  constructed  like  Fig.  40^; 
in  case  there  are  holes  in  one  leg  only,  as  in  Fig.  40^;  if  there 
are  no  holes  in  a  part  of  one  flange,  that  portion  of  the  templet 
may  be  omitted  altogether;  or  the  one  piece  may  contain 
layout  for  both  legs. 


FIG.  406.        FIG.  4oc.         FIG.  40^.    FIG.  406.    FIG.  4o/.      FIG.  4og. 
Templets. 

The  templet  for  the  top  of  a  channel  or  I  beam  is  a  plain 
flat  board.  For  the  web  of  the  latter  it  is  a  board  to  which 
are  nailed  cross  pieces  containing  the  holes  and  just  fitting 
the  fillets,  Fig.  40^.  Templets  for  channel  are  seen  in  Fig.  4o/. 

On  the  templet  is  marked  the  size  of  section,  length,  diameter 
of  holes,  identification  mark,  and  number  required. 

Templet  making  is  expensive  and  therefore  should  be  econ- 
omized as  far  as  possible. 

(1)  Design  as  many  pieces  as  possible  so  that  they  may  go 
through  the  rack  punch. 

(2)  If  there  are  two  members  of  the  same  length  but  slightly 
different  loads,  it  is  customary  to  make  them  alike  but   strong 
enough  for  either.     Often  a  great  deal  may  be  saved  by  bearing 
this  point  in  mind  during  the  design. 

(3)  If  pieces  are  not  alike,  they  may  be  made  enough   so 
that  a  single  templet  can  be  used  for  both.      For    example 


102  ELEMENTS  OF  STRUCTURAL  DESIGN 

the  stresses  in  the  laterals  of  a  bridge  decrease  toward  the 
center.  One  templet  will  do  for  all  panels,  however,  by  using 
the  same  sized  legs  throughout  and  varying  their  thickness 
and  by  omitting  certain  rivets;  the  templet  should  be  marked 
to  show  variations.  Cuts  occurring  in  one  member  but  not 
in  another  may  be  indicated  as  in  Fig.  40^. 

The  engineering  department  gives  measurements  in  either  of 
two  ways: 

(1)  Give    dimensions    sufficient    to    completely    determine 
everything. 

(2)  Give   general   center   to    center   distances,    size   of   all 
material,  number  of  rivets  required,  together  with  maximum 
and  minimum  edge  distances. 

(i)  is  generally  the  best  method  since  in  case  repair  or 
additions  are  decided  on,  (2)  gives  no  definite  knowledge  of 
the  location  of  the  rivets. 

A  templet  shop  is  usually  a  well-lighted  room  with  plenty 
of  space  for  full  size  layouts.  It  should  contain  a  full  assort- 
ment of  carpenter's  tools,  numerous  benches,  a  boring  machine, 
and  a  knife  for  cutting  off  material. 

Art.  41.     Methods  of  Cutting  Material  * 

(See  Art.  37  for  description  of  machines) 

Shapes  other  than  plates,  angles,  I  beams,  and  channels 
are  usually  sawn.  However,  squares  and  rounds  may  be 
sheared  by  a  special  blade.  One  important  point  comes  in 
here.  It  is  practically  impossible  to  shear  off  a  distance  less 
than  half  the  thickness  of  the  metal. 

Plates  are  cut  either  by  punching  out  and  chipping,  or  by 
one  of  the  shears.  The  latter  should  always  be  used  where 
possible,  as  the  former  is  very  expensive.  To  see  if  a  given 
plate  can  be  cut  by  the  shop  equipment,  draftsmen  ought  to 
have  a  scale  drawing,  such  as  is  shown  in  Fig.  41  a,  of  the  various 
shears.  Note  that  piece  must  be*  reversed  to  finish  shearing. 
A  trial  with  the  plate  drawn  to  the  same  scale  will  soon  show 
if  it  may  be  cut  off  in  the  machine.  If  impossible,  it  must  be 

*  Reference  for  Arts.  41-47,  Eng.  News,  Vol.  LV,  p.  356. 


FABRICATION  OF  STRUCTURAL  STEEL 


103 


punched  out  as  shown  in  Fig.  416,  and  chipped  off,  which  is 
very  expensive. 

Avoid  re-entrant  cuts,  abc,  Fig.  410.  Since  the  shear  cracks 
material  beyond  where  it  has  cut,  abc  must  either  be  punched 
out  and  chipped  or  else  a  hole  made  at  b  and  then  ab  and  be 
can  be  sheared.  This  is  expensive  on  account  of  extra  process 


FIG.  4ia. 

Diagram  of  Gate 
Shear. 


FIG.  416. 

Punching  Out 
Plate. 


FIG.  4  ic. 

Re-entrant 
Cut. 


FIG.  4id. 

Diagram  of  Angle 
Shear. 


involved.     Do  not  make  any  angle  much  less  than  90°,  as  such 
a  corner  tends  to  curl  up  when  shearing. 

Angles  are  usually  cut  by  the  angle  shears.  It  saves  a 
great  deal  of  time  and  often  obviates  shearing  entirely  if  they 
have  square  ends.  As  will  be  seen  by  a  study  of  Fig.  4  id, 
there  is  a  limit  to  the  skew  at  which  an  angle  may  enter  the 


Front.          Back.  Re-entrant 

FIG.  4is.  FIG.  4if. 


FIG.  41  g. 
Cuts  for  Various  Shapes. 


FIG.  4ih. 


tool.  If  beyond  the  limit,  angle  should  be  cut  off  square, 
and  one  leg  trimmed  in  plate"  shear  as  shown,  Fig.  410,  two 
processes  instead  of  one,  and  that  much  more  expensive. 

Fig.  4 if  shows  three  kinds  of  skew  cuts.     The  "  front  cut  " 
is  the  usual  one  and  angle  shears  are  designed  for  it.     The  "  back 


104  ELEMENTS   OF  STRUCTURAL  DESIGN 

cut  "  is  more  costly  but  can  be  done.  The  re-entrant  cut  is 
entirely  impracticable. 

An  I  beam  or  channel  may  be  cut  in  four  ways : 

(i)  Beam  Shears.  (2)  Coping  Machine.  (3)  Cold  Saw. 
(4)  Punching. 

(4)  is  expensive  and  is  done  only  where  the  other  equipment 
is  lacking.  (3)  does  good  work  but  takes  time,  (i)  and  (2) 
are  cheap  and  good  enough.  If  the  beam  is  to  be  cut  by  a 
plane  perpendicular  to  the  web  but  beveled  to  the  plane  of 
the  flange,  it  may  be  cold  sawn  or  coped  out  approximately 
to  requ  red  lines  as  shown  in  Fig.  41  g.  If  cut  by  a  plane  per- 
pendicular to  flange  but  beveled  to  web,  it  may  be  cut  by  cold 
saw,  if  latter  is  large  enough  or  coped  out  to  lines  shown  in 
Fig.  4ih. 

Important  principles  developed  here  are : 

(1)  Avoid  small  cuts. 

(2)  Do  not  use  re-entrant  angles. 

(3)  Keep  cuts  to  a  minimum. 

(4)  Use   square   ends   unless   important   reasons   determine 
otherwise. 

Art.  42.     Methods  of  Bending 

Small  rods  and  thin  plates  are  bent  by  drawing  into  position 
in  the  assembled  structure.  In  other  cases  the  part  must  be 
heated.  If  much  bending  of  a  certain  radius  is  required,  two 
dies  of  that  radius  are  prepared,  one  of  which  is  fastened  to  a 
plunger.  The  heated  section  is  placed  between  them  and  the 
stroke  of  the  plunger  completes  the  job.  Or  the  hot  shape 
is  hammered  or  forced  by  levers  into  the  desired  form,  the 
templet  being  used  as  a  pattern. 

A  shape  may  be  bent  in  a  plane  containing  its  axis  or  so 
as  to  change  the  section.  As  an  example  of  the  latter  class 
let  us  take  the  connection  of  two  I  beams  framing  together 
at  an  oblique  angle,  Fig.  420.  If  angle  of  intersection  lies 
between  85  and  95  degrees,  it  is  customary  to  use  a  bent  angle. 
Otherwise  a  plate  is  bent  the  required  amount.  It  is  very 
difficult  to  make  a  sharp  corner  of  the  latter  construction. 
Generally  it  will  be  rounded  to  a  radius  of  a  few  inches. 


FABRICATION  OF  STRUCTURAL  STEEL 


105 


Crimping,  Fig.  42^,  is  the  offsetting  of  an  angle  and  is  best 
done  by  a  machine.. 

Loop  rods  may  be  either  circular  or  square  in  section.  The 
latter  gives  better  contact  and  is  preferred  for  that  reason. 
They  are  used  only  for  the  purpose  of  carrying  tension  between 
two  pins  and  are  commonly  made  adjustable  as  explained  in 
Art.  43.  To  fasten  them,  the  rod  is  bent  back  on  itself  and  firmly 
welded,  the  distance  between  pin  and  weld  being  equal  to 


FIG.  42a.  FIG.  426.  FIG.  420.  FIG.  42^. 

Bent  Connections.   Crimped  Angle.     Single  Loop  Rod.  Double  Loop  Rod. 

two  or  three  diameters  of  the  former.     This  fork  is  sometimes 
made  double  as  shown  in  Fig.  42^. 

Hangers  are  short  members  carrying  a  direct  load.  A 
common  construction  is  to  make  them  like  a  short  non-adjustable 
rod.  The  breaking  of  a  hanger  supporting  a  floor  beam  in  a 
deck  railroad  bridge  near  Forest  Hills,  Mass.,  on  the  Boston 
and  Providence  R.  R.  caused  a  bad  wreck,  Art.  69,  and  hangers 
have  not  been  used  in  first-class  construction  since.  Indeed, 
in  a  well-  designed  structure, 
little  reliance  is  placed  on  a 
weld  joint,  its  most  important 
allowable  duty  being  for  wind 
stresses. 

Buckle  plates  are  plates  stiff- 
ened by  pressing  between  large 
dies  into  form  shown  in  Fig.  420. 

When  bent  cold  within  the  elastic  limit,  the  length  of  the 
neutral  axis  remains  unchanged;  above  it,  the  tension  side 
stretches  while  the  compression  side  does  not  alter  very  much. 
When  bent  hot,  much  depends  on  the  manipulation  of  the 
metal  by  the  blacksmith. 

Forge  work  injures  steel  considerably,  although  subsequent 
annealing  may  remove  some  of  this. 

A  shape  can  be  bent  to  almost  any  radius,  but  the  sharper 


FIG.  426. — Buckle  Plates. 


106  ELEMENTS  OF  STRUCTURAL  DESIGN 

this  becomes,  the  greater  the  cost  and  the  loss  of  strength 
and  the  less  desirable  is  the  appearance. 

We  find  then  that  it  is  difficult  to  do  good  work  in  bending; 
that  it  is  wasteful  and  weakening.  This  conclusion  will 
apply  to  all  hand  forgings,  hence  hand  work  in  the  forge  shop 
is  to  be  made  a  minimum. 


Art.  43.    Process  for  Upsetting 

This  has  already  been  defined  in  Art.  25.  We  there  spoke 
of  one  of  the  two  cases,  the  other  being  that  of  eyebars.  The 
upset  for  the  screw  end,  whether  the  shape  be  round,  square, 
or  flat,  is  made  round  and  of  sufficient  size  after  thread  is  cut 
to  give  at  least  20%  excess  of  area,  this  being  to  allow  for  loss 
of  strength  due  to  forging,  as  explained  in  preceding  article. 
The  length  of  the  rod  necessary  to  form  this  upset  may  be 
readily  computed  if  we  allow  10%  for  losses  due  to  heating 
and  trimming. 

Adjustable  members  are  sometimes  made  by  cutting  in  two- 
an  ordinary  member,  upsetting  and  threading  each  end  so  cut, 
and  inserting  a  turnbuckle,  Fig.  430,  or  sleeve-nut,  Fig.  436. 


FIG.  430. — Turnbuckle.  FIG.  436. — Sleeve  Nut. 

In  each,  the  thread  must  be  right  hand  in  one  half  and  left 
in  the  other.  The  former  has  the  advantage  that  the  position 
of  the  ends  may  be  determined  by  inspection.  Eyebars  are 
made  by  placing  a  bar  in  a  furnace,  heating  the  end  for  several 
feet,  and  upsetting.  Bar  is  next  annealed,  that  is,  heated  to  a 
dull  cherry  red  and  then  allowed  to  cool  very  slowly  after 
which  they  are  taken  to  the  straightening  rolls.  Sometimes 
a  hole  somewhat  smaller  than  final  is  punched  while  metal 
is  hot  and  then  it  is  drilled  to  exact  size,  or  sometimes  entire 
hole  is  drilled  at  one  operation. 

The  bar  now  presents  the  appearance  shown  in  Fig.  43^, 
The  diameter  of  the  pinhole  is  commonly  made  1/50  to  1/32 


FABRICATION  OF  STRUCTURAL  STEEL  107 

of  an  inch  larger  than  size  of  pin.  The  thickness  of  the  bar  is 
usually  the  same  throughout,  but  the  head  is  sometimes 
thicker  than  the  body  of  the  bar.  The  net  area  of  the  hole 
should  be  at  least  30%  in  excess  of  the  area  of  the  bar  itself. 
The  head  is  usually  made  of  arcs  of  circles,  as  shown. 


JJL 


FIG.  43C. — Eyebar. 

Length  of  upset;  diameter  of  thread;  dimensions  of  turn- 
buckles,  sleeve-nut,  and  eyebar  heads  may  differ  a  little,  each 
company  having  its  standards. 

An  adjustable  member  may  also  be  made  by  upsetting  and 
threading  each  end  and  attaching  thereto  a  clevis  nut  which 
connects  with  a  pin  which  in  its  turn  passes  through  the  con- 
nection plate.  Method  of  manufacture  is  as  follows:  The 
iron  or  steel  is  first  piled  up  as  shown  in  Fig.  43^.  In  the  die 
under  the  steam  hammer,  it  takes,  after  being  heated,  the 
shape  seen  in  Fig.  430.  Reheated  and  hammered  in  another 
die  it  takes  the  form  of  Fig.  43/.  The  smith  then  bends  the 


Hill    II    Hill          t—Q^3         O=o=O 

FIG.  43<J.  FIG.  43^.  FIG.  43/.  FIG.  43^. 

Successive  Stages  in  Manufacture  of  Clevis  Nuts. 

ends  close  to  the  center  until  they  become  parallel.  The 
holes  for  the  pin  are  next  drilled  and  the  end  is  threaded,  and 
the  nut  appears  in  its  finished  form  as  shown  in  Fig.  43^.  Each 
company  has  its  own  standards,  the  same  clevis  doing  for  several 
sizes  of  threads  or  pins,  the  details  being  such  as  to  make  the 
nut  stronger  than  the  bar. 


108  ELEMENTS  OF  STRUCTURAL  DESIGN 

Art.  44.    Methods  for  Making  Holes 

(See  Art.  37  for  machines) 

Holes  may  be  either  punched  or  drilled. 

A  punch  is  likely  to  break  if  metal  is  thicker  than  diameter 
of  hole.  Do  not  try  partial  holes,  Fig.  440;  it  is  difficult  to 
secure  good  work  and  the  punch  will  not  long  endure  this 
treatment. 

In  detailing  members  where  rack  or  multiple  punch  will 
be  used,  care  must  be  taken  to  keep  rivets  in  horizontal  and 
vertical  lines.  There  is  a  minimum  allowable  distance  :n  each 
direction,  due  to  the  construction  of  the  machine.  If  spacing 
is  less  than  that,  templets  must  be  used,  adding  quite  a  bit 


I 

1 

I 

1 

FIG.  440. — Partial  Hole.  FIG.  44^. — Typical  Matching  of  Holes. 

to  the  expense.  Rack  or  multiple  punching  does  not  pay 
where  there  are  but  few  alike,  for  small  pieces,  or  for  skew 
work.  Other  cases  should  be  so  arranged  that  shop  can  use 
it  if  they  so  elect. 

Punching  is  the  cheaper  process,  but  it  distorts  and  injures 
metal,  and  holes  are  likely  to  match  poorly.  Further,  when 
several  pieces  are  joined  together,  the  resulting  hole,  Fig.  44^, 
is  irregular  and  rivet  does  not  thoroughly  fill  it.  To  overcome 
these  objections,  we  may: 

(1)  Drill  from  solid,  or 

(2)  Enlarge  by  reaming. 

For  the  former,  there  are  four  methods: 
(10)  Pneumatic  drill. 
(ib)  Drill  press. 
(ic)   Radial  drills. 
(id)  Boring  machines. 

(ib)  and  (id)  are  much  alike,  the  latter  being  used  for  large 
holes,  as  already  noted.  (10)  is  portable  but  not  as  effective 


FABKICATION  OF  STRUCTURAL  STEEL  109 

as  (ib).  (ic),  however,  combines  the  good  points  of  both. 
Pieces  may  be  laid  down  underneath  the  raolial  drills,  while 
the  latter,  attached  to  a  small  gantry  crane,  are  moved  along 
it,  drilling  holes  as  they  go. 

Now  drilling  from  solid  is  quite  expensive  and  is  seldom 
done  except  for  cast  iron  or  where  metal  is  almost  as  thick  as 
diameter  of  the  rivet.  The  advantages  of  drilling  without  ks 
disadvantages  may  be  obtained  by  sub-punching  and  reaming, 
that  is,  by  punching  a  hole  about  J  inch  smaller  than  original 
diameter  of  rivet,  and  then  enlarging  it  to  1/16  inch  more. 
This  enlargement  may  be  effected  by  using  either  of  first  three 
'  machines  mentioned  in  drilling,  with  the  same  or  different 
tools.  For  reaming  also  the  radial  machines  are  best. 

Reaming  is  done  after  assembly  because  it  insures  a  good 
rivet  and  takes  care  of  several  holes  at  once.  It  is  often  required 
for  field  rivets.  There  are  two  methods  of  doing  this:  by 
reaming  all  parts  which  connect,  to  a  common  iron  templet; 
also  to  put  them  together  at  shop,  ream,  and  then  matchmark, 
so  the  same  connection  will  be  made  in  the  field.  The  latter, 
while  expensive,  is  obviously  preferable  and  is  now  quite  common. 

Pinholes  in  eyebars  or  built-up  members  are  punched  out 
and  then  enlarged  in  a  boring  machine.  A  slotted  hole,  Fig. 
6ib,  may  be  cut  out  by  a  special  punch,  or  two  holes  may  be 
made  at  each  end,  and  remainder  cut  out  by  shaper. 

Important  principles  are: 

(1)  Avoid  partial  holes. 

(2)  Holes   having   a   $ameter   greater   than    thickness   of 
material  must  be  drilled  to  avoid  breaking  punch. 

(3)  Different  sized  holes  are  a  fruitful  source  of  expense 
and  annoyance.     See  also  Art.  47. 

Art.  45.    Layout  and  Assembly 

Material  which  requires  bending  is  sent  to  blacksmith's  shop 
and  thence  to  the  room  of  the  layer-out.  Straight  stuff  passes 
directly  thereto.  Some  pieces  will  be  taken  to  spacing  tables, 
others  punch-marked  by  measurements  on  steel  itself  and 
perhaps  the  larger  part  will  be  laid  off  by  templet,  Art.  40. 

Layer-out  is  supposed  to  be  as  economical  as  possible  of  mate- 


110  ELEMENTS  OF  STEUCTURAL  DESIGN 

rial.  In  a  large  job,  involving  a  great  deal  of,  let  us  say,  1 2"  X  f " 
plates,  it  will  be  ordered  in  about  30  foot  lengths.  It  may  be 
that  there  are  many  different  lengths  and  hundreds  of  pieces 
to  be  cut  from  this.  Perhaps  there  is  only  one  possible  way 
of  doing  this.  The  bills  of  material,  Art.  63,  give  what  he  is 
to  cut  with  as  little  waste  as  possible.  He  must  also  make 
necessary  allowances  for  fitting  and  milling.  Irregular  plates 
may  often  be  sheared  to  save  a  great  deal  of  material.  Thus 
a  plate  like  Fig.  450  should  be  cut  out  as  seen  in  Fig.  456. 


A 

V 

\/\\ 

•      /;             \      A 

FIG.  450.  FIG.  456. 

Method  of  Shearing  Skew  Plates. 

The  material  is  next  sheared,  Art.  41,  then  punched  or 
drilled,  Art.  44,  and  passed  on  to  assembly.  Surfaces  which 
will  afterwards  be  in  contact  now  receive  a  coat  of  paint.  The 
different  parts  are  next  "  assembled/'  that  is,  fitted  together 
and  fastened  with  a  sufficient  number  of  bolts  to  hold  firmly 
while  rivets  are  being  driven.  Though  forbidden  by  most 
specifications,  holes  which  do  not  fit  well  are  persuaded  by 
the  use  of  "  drift  pins  "  (pointed  pieces  of  steel),  backed  up 
by  sledge  hammers.  A  better  way  and  one  which  is  now  used 
more  and  more,  is  to  sub-punch  and  ream  out  after  assembly 
(Art.  44). 

It  is  particularly  desirable  for  this  class  of  work  that  drawings 
should  be  clear,  views  properly  shown,  and  notes  explicit  and 
easily  understood. 

Art.  46.    Fastenings  for  Steel  Work 

While  there  are  rivets  having  different  styles  of  heads  as 
shown  in  Fig.  460,  they  are  not  common  in  structural  work, 
the  button  head  being  the  universal  type.  This  is  slightly 
less  than  a  hemisphere.  It  may  be  modified  as  indicated  in 
Art.  47- 

Bolts,  Art.  25,  7&,  are  also  used  in  steel  work.    The  hexagonal 


FABRICATION   OF  STRUCTURAL  STEEL  111 

head  is  lighter  and  is  preferable  on  account  of  its  better  appear- 
ance and  lesser  clearance  required   for  tightening.     Unlike  the 
wood  the  hole  in  the  steel  must  be  made  some  larger,  and  since 
the  bolt  is  not  heated  for  driving,  it  does  not  fill  the  irregulari- 
ties as  does  the  rivet.   This  objection  may  be  overcome  by  drilling 
the  hole  and  turning  the  bolt  a  few  thou- 
sandths smaller.    It  is  then  called  a  "  turned          ^      0 
bolt." 

A  tap  bolt  in  steel  corresponds  to  a  lag 
screw  in  wood,  "it  may  have  a  square  or 
hexagonal  head  but  no  nut,  and  is  used  to  FIG.  460. 

fasten    one    object   to    another  where   it   is  Unusual  Rivet  Heads, 
impracticable  to  get  at  the  nut   end.      The 
piece  that  carries  the  screw  end  is  said  to  be  tapped,  that  is, 
it  has  a  hole  bored  in  it  a  little  more  than  the  length  of  the 
bolt  and  a  female  thread  is  then  turned  thereon. 

A  stud  bolt  is  a  tap  bolt  with  a  thread  and  nut  instead  of 
a  head  on  the  outer  end.  A  hook  bolt,  Fig.  466,  has  instead  of 
its  head  a  form  bent  as  shown.  It  is  often  used  in  fastening 
ties  to  the  beams  on  which  they  rest.  A  U  bolt  is  made  as 
shown  in  Fig.  460. 


FIG.  466.  FIG.  460.  FIG.  46^.  FIG.  460.  FIG.  46/. 

Hook  Bolt.          UBolt.         Ragged  Bolt.    Swedged  Bolt     Expansion  Bolt. 

Foundation  bolts  are  made  in  various  styles,  although  the 
plain  bolt  is  about  as  good  as  any  of  them  and  much  more 
economical;  however,  it  is  sometimes  threaded;  sometimes 
ragged,  Fig.  46 d,  swedged,  Fig.  46^,  or  is  made  as  shown  in 
Fig.  46/5  expansion  bolt. 

Pins  are  large  specially  designed  bolts  with  both  ends  threaded 
and  a  nut  placed  on  each.  The  usual  type  of  a  pin  is  shown 
in  Fig.  46g.  Each  company  has  its  standards,  but  the 
distance  fa  is  usually  equal  to  the  metal  which  it  grips,  while 
/i  and  fe  are  each  made  equal  to  thickness  of  the  nut  plus  a 


112 


ELEMENTS  OF  STRUCTURAL  DESIGN 


quarter  of  an  inch  or  a  little  more.  The  nut  is  always  hexagonal, 
and  has  a  long  diameter  of  about  4/3  that  of  the  pin  and 
thickness  of  ij".  d^  is  about  3/4  of  d\. 

Pins  are  turned  and  threaded  from  rounds  of  medium  steel 
1/16  to  3/16"  larger,  this  amount  varying  with  shop  practice 
and  with  size  of  pin. 

Sometimes  a  cast-iron  washer  about  i"  in  thickness  and 
slightly  larger  than  the  large  diameter  of  the  pin  is  placed 
at  one  end.  In  that  case  12  and  either  l\  or  /3  are  each  made 


FIG.  46g.—  Typical  Pin.     FIG.  46h—  Lomas  Nut.       FIG.  46*.—  Special  Pin. 


}"  longer.  The  idea  of  this  is  to  provide  for  variations  in  grip 
from  its  computed  length.  A  still  better  method  of  accom- 
plishing the  same  purpose  is  to  use  the  Lomas  nut,  Fig.  46^,  which 
is  about  the  same  size  as  the  usual  pin  nut  except  it  has  a 
recess  of  \"  to  f  "  as  shown. 

Occasionally,  for  the  purpose  of  providing  a  smaller  hole 
in  a  plate,  the  pin  is  turned  to  a  lesser  diameter  usually  to  that 
of  the  thread.  This  may  be  done  on  either  or  both  ends,  the 
latter  case  being  shown  on  Fig.  462'.  Or,  at  the  support,  projec- 
tions beyond  the  thread  may  be  made  in  order  that  jacks  be 
used  to  lift  the  bridge. 

Suppose  in  Fig.  46;  that  it  is  necessary  to  keep  the  outer 
eyebars  2"  outside  of  the  inner,  as  shown.  If  pin  and  nut  as 

given  above  be  used,  the  eyebars 
might  move  around  or  rattle. 
It  then  becomes  necessary  to 
use  washer  fillers,  Fig.  46^. 

The  p  ate  is  usually  \"  thick, 
and  the  inside  diameter  is 
about  3/16"  more  than  that  of 
the  pin.  In  this  case  we  would 

order,  "2  Pis.  is"xi"Xif","  the  15"  being  given  as  the 
plate  width  since  the  same  size  pins  are  often  used  throughout 
a  job,  hence,  all  plate  for  this  purpose  will  have  the  same  width. 


o 


FIG.  467. 
Pin  Joint. 


FIG.  46k.— Washer 
Filler  for  Joint. 


FABBICATION  OF  STRUCTURAL  STEEL 


113 


In  order  to  facilitate  erection  and  protect  the  threads  of 
the  pin,  a  point  and  a  cap  must  be  provided.  The  point  is 
called  a  pilot  nut  and  may  be  either  short  or  long  as  shown  in 
Figs.  461  and  m.  It  is  cast  of  iron  or  steel  and  has  its  outside 


FIG.  461.      FIG.  46m. 
Short.    Pilot  Nuts.    Long. 


FIG.  46n. 
Driving  Nut. 


FIG.  460. 
Pin  Ready  for  Driving. 


diameter  equal  to  that  of  the  pin,  while  a  female  thread  to 
fit  that  on  the  end  of  the  pin  is  turned  inside.  The  cap  is  called 
a  driving  nut  and  is  shown  in  Fig.  46^.  As  in  the  pilot  nut, 
the  driver  fits  both  at  the  thread  and  on  the  outside.  The 
pilot  and  driving  nuts  now  give  the  pin  the  appearance  shown 
in  Fig.  460,  and  render  erection  quite  easy. 

Cotter  pins  are  commonly  used  with  clevis  nuts.  They 
derive  their  name  from  the  cotter,  a  small  piece  of  bent  wire 
as  shown  in  Fig.  46^,  which  is  inserted  at 
one  end  to  prevent  the  pin  from  coming 
out.  The  other  end  is  about  J"  larger 
in  diameter  than  the  body,  the  whole 
pin  appearing  as  shown  in  Fig.  469.  /3  is 
usually  made  \"  ,  1%  a  trifle  more  than  the 
thickness  of  metal  to  be  gripped,  while  l\ 
is  about  i".  The  material  is  ordered  exact  to  length  and  of  a 
size  of  round  equaling  diameter  of  head.  It  is  then  turned 
down  and  a  7/1  6"  hole  for  a  f  "  cotter  pin  placed  as  shown. 
Fig. 


l 


FIG.  46/>. 
Cotter. 


FIG.  46?. 
Cotter  Pin. 


Art.  47.    Methods  for  Riveting 

(For  machines,  see  Art.  37) 

The  rivets  described  in  preceding  article  may  be  driven  by: 

(i)  Machine  riveter.  (2)  Pneumatic  hand  riveter. 

(3)  Hand  tools. 

The  hot  rivet  is  "  entered  "  into  hole  from  one  side  and 
firmly  held  there  until  tool  on  other  side  has  upset  the  head. 


114  ELEMENTS  OF  STRUCTURAL  DESIGN 

At  each  end  is  a  bar  with  a  nearly  hemispherical  recess  as  seen 
in  Fig.  470.  Two  sides  may  be  cut  away  or  an  octagonal  bar 
used.  The  head  mashes  up  so  that  f  "  should  be  employed 
instead  of  J"  in  figuring  clearances. 

In  (i),  both  ends  are  held  by  machine,  large  power  is  exerted, 
and  it  makes  an  excellent  rivet  very  economically.  Hence 
always  design  so  a  machine  riveter  can  be  employed  as  much 
as  possible. 

In  (2),  cylindrical  end  is  upset  by  the  riveter.  The  other 
end  may  be  held  by  a  short  heavy  bar  about  in  line  with  rivet, 
by  a  longer  piece  called  a  dolly  bar,  Fig.  476,  used  as  a  lever, 
or  by  a  pneumatic  "  holder-on."  The  latter  is  a  bar  with  a 
die  in  the  end  which  is  forced  into  position  against  the  rivet 


FIG.  470.— Rivet  Die.  FIG.  476.— Dolly  Bar. 

and  held  there  by  pneumatic  pressure.  There  are  several 
forms  of  holding  bars  in  order  to  provide  for  driving  in  difficult 
locations;  they  may  be  bent  or  inclined  at  an  angle  to  the 
rivet. 

This  process  makes  good  rivets  but  they  are  not  as  strong 
as  those  driven  by  machine  if  proper  care  is  used  in  adjustment 
of  the  latter.  The  advantages  of  this  process  are  the  portability 
of  the  riveter  and  its  adaptability  to  almost  any  condition. 

In  (3),  same  tools  are  employed  on  holding  end.  The 
driving  is  accomplished  by  a  die  set  in  a  handle.  This  die 
is  much  like  those  we  have  already  studied  except  that  it  is 
quite  short  and  head  is  shaped  to  rece've  the  blows  of  the  sledges. 
Resulting  rivets  are  weaker  and  more  expensive  than  those 
driven  by  air  and  this  method  is  now  seldom  used;  only  in  small 
erection  work  and  in  locations  not  accessible  to  the  pneumatic 
riveter. 

In  driving  the  rivet,  it  is  pushed  in  on  the  holding  side 
and  upset  on  the  driving  side.  It  is  best  when  it  can  be  entered 
and  driven  either  way.  In  machine  driving,  some  feet  are 
required  in  both  directions  for  clearance  in  line  with  rivet  axis, 
rather  more  being  necessary  on  driving  side.  Measurements 


FABRICATION  OF  STRUCTURAL  STEEL 


115 


will  vary  for  different  machines,  and  actual  details  of  riveter 
should  be  consulted  in  doubtful  cases.  For  pneumatic  riveting, 
24"  is  desirable  on  driving  side  and  12"  on  holding,  but  both 
can  be  lessened  by  special  tools,  a  riveter  of  this  type  bringing 
former  down  to  12".  This  applies  to  cases  where  rivet  is 
backed  by  a  pneumatic  "  holder-on."  This  is  not  always 
necessary,  but  should  be  employed  if  pneumatic  process  is  used 
in  driving  long  rivets.  On  the  holding  side  distance  can  usually 
be  made  as  small  as  entering  of  rivet  will  permit.  The  latter 
applies  to  hand  riveting  also,  but  on  the  driving  side,  room 
must  be  provided  to  swing  sledges. 


FIG.  47c.      FIG.  47<f.        FIG.  470. 

Transversely  to  the  axis  of  the  rivet,  clearance  must  be 
provided  for  die  as  already  described.  In  certain  locations, 
parts  of  machine  are  to  be  cleared.  Consider,  as  an  example, 
the  vertical  rivets  in  the  flanges  of  plate  girders,  as  seen  in  Fig. 
47c.  Here  the  distance  d  for  machine  driving  shou  d  be  about 
2"  and  e  2\".  In  determining  clearances,  consider  only  rivet 
heads  that  are  close  by,  say  within  2  or  3  inches.  Those  8  or 
10"  away  may  be  ignored  entirely.  Thus  in  Fig.  47^,  to  drive 
a  after  other  rivets,  consider  head  b  but  not  d,  and  probably 
not  c.  This  interference  might  be  prevented  by  staggering 
as  in  Fig.  470.  Following  table  gives  approximate  value  for 
clearances : 


Hand  Driving. 

Machine  Driving. 

Diam.  Rivet. 

Minimum. 

Desirable. 

Minimum. 

Desirable. 

I" 

7// 
8 

it" 

It" 

It" 

I" 

l" 

It" 

It" 

it" 

l" 

it" 

it" 

it" 

if" 

Clearance  required  for  driving  rivets,  for  erection,  or  perhaps 
for  other  purposes,  may  require  a  head  somewhat  less  in  height 


116  ELEMENTS  OF  STRUCTURAL  DESIGN 

than   full  head   described  in  preceding   article.     It  may  be, 
Fig.  47/: 


FIG.  47/.  —  Special  Heads. 
1234 
Flatten       Flatten      Flatten    Countersunk 
to  f".          to  J".         to  |".     and  chipped. 

(1)  Head  flattened  to  f  ". 

(2)  Head  flattened  to  \n  ',  and  hole  countersunk  to  obtain 
the  necessary  strength. 

(3)  Head  flattened   to  £".     Here   rivet  is   pounded   down 
about  flat  but  is  not  chipped  off,  care  being  taken  that  the  head 
does  not  exceed  |". 

(4)  Head  countersunk  and  chipped  flat. 

Note  well  —  (i)  involves  hammering  down  rivet  either  by 
hand  or  a  flat  die.  (2)  and  (3),  hammering  down  and  boring 
out  of  hole  (countersinking).  (4)  means  hammering  with 
special  die,  countersinking,  and  chipping  if  special  head  is  on 
the  driving  side  or  a  countersunk  head  rivet  and  countersinking 
if  on  entering  side.  From  the  above,  it  will  be  seen  that  counter- 
sinking rivets  adds  largely  to  the  cost. 

Points  to  be  kept  in  mind  are  : 

(1)  Be   sure   to   provide   sufficient   room   in   all   directions 
around  riveter.     Be  a  little  liberal  in  cases  where  there  is  close 
work  on  more  than  one  side.     Provide  for  entering  and  holding 
one  way  and  driving  on  the  other.     Proceed  similarly  for  bolts 
except  to  substitute  clearance  for  turning  nut  in  place  of  driving. 

(2)  If   thickness   of    material  gripped  by  rivet   (grip),   be 
more  than  four  diameters,  there  is  likelihood  of  unsound  work. 
Avoid  therefore  long  rivets. 

(3)  Countersunk  rivets  should  be  reduced  to  a  minimum 
and  if  possible  eliminated  altogether.     The  additional  operations 
are  but  a  small  part  of  the  expense;   it  is  the  changing  of  dies 
and  the  care  necessary  to  look  after  these  special  rivets. 

(4)  Different  sized  rivets  in  the  same  piece  mean  different 
dies  for  both  punching  and  riveting.     This  is  costly  and  a  source 
of  much  bother.     To  avoid  proceed  as  follows:    For  each  job, 


FABRICATION  OF  STRUCTURAL  STEEL  117 

pick  out  a  certain  sized  rivet,  usually  the  largest  which  may 
be  driven.  This  is  about  }"  for  small  work,  f"  for  medium, 
and  i"  for  heavy  construction.  Design  sections  so  that  one  of 
these  may  be  used  throughout.  Sometimes  it  will  be  cheaper 
to  increase  a  section  and  use  more  metal  than  to  have  varying 
sizes  of  rivets.  When  the  connections  between  parts  of  a  structure 
are  few,  different  sizes  may  then  be  used  in  those  parts.  In 
this  case,  the  line  of  demarcation  should  be  so  chosen  that  the 
fewest  pieces  in  number  and  the  smallest  in 
size  will  have  to  be  punched  and  riveted  twice.  «*0* 

(5)  If  rivet  spacing  exceeds  6"  or  16  times          pIG>  47g 
the  thickness  of  the  thinnest  outside  plate,  there    Buckling  of  Plate, 
is  danger  of  buckling  as  shown  in  Fig.  47^. 

(6)  Use  only  as  many  rivets  as  are  necessary  for  strength 
and  stiffness.     Shop  driving  alone  costs  2j£  apiece,  and  total 
expense  is  not  far  from  5^. 


Art.  48.    Inspection,  Painting,  and  Shipment 

Inspection  is  of  two  kinds;  that  controlled  by  the  structural 
concern  and  that  in  the  interest  of  the  purchaser.  We  shall 
consider  inspection  of  material  as  outside  of  this  work. 

The  inspector  for  the  structural  company  examines  each 
piece  and  ascertains  if  outside  dimensions  and  open  holes  agree 
with  drawings.  His  principal  objects  are: 

(1)  To  ensure  acceptance  of  the  piece  by  purchaser. 

(2)  To   correct   deviation   from   plans  which  would   delay 
completion  in  case  his  concern  erects  bridge. 

The  work  of  the  purchaser's  inspector  is  much  more  difficult. 
Moreover,  he  is  judge  between  structural  company  and  pur- 
chaser as  to  inspection  and  fulfillment  of  contract  as  shown 
in  the  plans  and  specifications.  His  field  is: 

(1)  To  allow  only  approved  material  to  be  used.     Ordinarily 
this  too  has  been  inspected. 

(2)  To  ensure  agreement  of  material  with  that  called  for 
by  strain  sheet. 

(3)  To  go  over  joints  and  ascertain  if  pieces  will  fit  together 

*  Reference  for  Shipping  and  Erection,  Eng.  News,  Vol.  LV,  p.  381. 


118  ELEMENTS  OF  STRUCTURAL  DESIGN 

in  the  field.  Not  only  should  measurements  be  compared  with 
those  on  the  drawings,  but  the  latter  should  themselves  be 
checked  with  one  another. 

(4)  To  enforce  specifications  in  regard  to  workmanship. 
Material  must  be  straight,  holes  properly  punched,  and  surfaces 
inaccessible  after  assembly  painted.  Inspector  should  watch 
milling,  boring,  planing,  and  riveting,  testing  the  latter  by 
hammer  to  be  sure  that  they  are  tight. 

(5')  Just  before  painting,  it  his  duty  to  make  a  detailed 
comparison  of  each  piece  with  plan,  and  have  any  errors  cor- 
rected. 

(6)  To  inspect  painting,  weighing,  and  shipment. 

On  important  jobs  there  may  be  an  inspector  of  erection. 
His  duties  will  be  to  see  that  steel  work  has  not  been  injured 
in  transit,  that  pieces  are  put  in  proper  position,  and  all  field 
rivets  are  well  driven. 

Material  should  be  cleaned  of  rust  before  painting.  On 
important  work,  it  may  be  removed  by  pickling  or  sand  blast; 
it  is  sometimes  taken  off  by  a  coat  of  gasoline  before  the  paint. 

Paint  is  usually  applied  by  hand  with  a  brush.  It  may 
be  done  by  compressed  air,  which  sprays  paint  on  the  steel,, 
(also  on  anything  else  in  the  vicinity).  It  is  wasteful,  unhealthy, 
and  does  not  do  the  work  as  well  but  is  economical  of  labor. 
Pins,  pin  holes,  screw  threads,  and  rollers  should  be  coated 
with  white  lead  and  tallow. 

Steel  is  next  weighed  and  this  compared  with  computed 
weight,  a  variation  of  i\%  being  allowed.  It  is  then  loaded 
on  cars  and  shipped  to  its  destination. 

We  shall  take  up  details  of  preparing  pieces  for  shipment 
only  so  far  as  it  concerns  designer  and  draftsman.  Pieces 
less  than  40  feet  long,  8  feet  wide,  and  9  feet  high  may  be 
shipped  almost  anywhere.  If  the  width  or  height  of  a  piece 
exceeds  these  limits,  examine  clearance  diagram,  Art.  50,  50,. 
for  roads  over  which  the  job  must  travel.  Longer  parts  may 
be  supported  on  two  cars.  Pieces  as  long  as  130  feet  may  be 
carried  by  inserting  idler  or  spacing  cars.  For  such  lengths, 
conditions  on  curves  must  be  investigated.  Plate  girders  are 
placed  upright  on  blocks  about  6"  high  to  which  they  are 
firmly  braced. 


FABRICATION  OF  STRUCTURAL  STEEL  119 

The  following  points  should  be  borne  in  laind  when  shipping : 

(1)  Pieces  which,   like  long  plate  girders,   are  difficult  to 
handle,  should  be  shipped  so  that  turning  end  for  end  at  site 
will  be  avoided. 

(2)  Small  parts  are  likely  to  be  lost  in  shipment;    they 
may  be  boxed  up,  bolted  together,  or  fastened  onto  a  piece 
with  which  they  connect. 

(3)  Ship  projecting  plates  or  shapes  only  when  necessary 
to  avoid  expensive  field  riveting;    otherwise  they  may  suffer 
injury  or  interfere  with  economical  shipment. 

(4)  Freight  rates  run  about  as  follows:    The  minimum  rate 
per  pound  can  be  obtained  when  loaded  with  not  less  than  30,000 
for  one  car  or  45,000  for  two.     If  cars  are  all  occupied,  not 
less  than  these  amounts  must  be  paid  for.     If  only  a  portion 
of  one  car  be  taken,  shipment  is  made  at  "  less  car  load  "  rates 
which  are  higher  per  pound.     It  is  hence  sometimes  better, 
in  spite  of  the  objectionable  field  riveting,  to  ship  a  small  job 
"  knocked  down  "  (in  small  pieces)  and  pay  pound  prices  for 
it  rather  than  full  car  rates.     Remember,  however,  that  the 
latter  is  prompter  and  less  likely  to  result  in  the  loss  of  a 
piece,  while  the  former  is  much  easier  to  team  and  to  handle. 

(5)  Sometimes  purchaser  pays  freight.     Do  not  forget  to 
guard  the  interests  of  your  client  as  far  as  it  is  honorable  to  do  so. 

Shipping  bills  are  described  in  the  next  chapter,  Art.  65. 
They  are  used  as  a  guide  by  inspector,  shipper,  and  erector. 
When  everything  on  this  bill  has  left  the  shop,  its  part  of  the 
contract  is  completed.  In  the  next  article,  we  shall  take  up 
the  work  at  the  final  site. 

Art.  49.    Erection  * 

Assembling  the  structure  on  its  site  and  fastening  together 
is  styled  the  erection.  In  this  article,  we  shall  describe  methods 
for  plate  girders,  viaducts,  and  simple  bridge  trusses.  Processes 
peculiar  to  other  types  will  be  considered  in  chapter  dealing 
with  same. 

The  heavy  weights  may  be  handled  by  block  and  tackle, 
jacks,  gin-poles,  derricks,  gallows  frames,  and  travelers. 

*  See  Dubois'  "Mechanics  of  Engineering,"  Vol.  II,  Chap  XIII. 


120 


ELEMENTS    OF   STRUCTURAL  DESIGN 


Hydraulic  jacks  have  a  short  stroke  and  are  not  thoroughly 
reliable.  On  account  of  the  latter,  blocking  must  always  be 
used  to  take  up  the  lift.  They  may  be  had  with  a  capacity  of 
800,000  pounds. 

A  gin-pole,  Fig.  490,  is  a  simple  strut  of  timber  or  steel, 
guyed  by  two  or  more  ropes  at  the  top  and  supported  at  the 
bottom.  The  hoisting  rope  runs  from  a  crab  near  the  foot 
over  a  sheave  at  the  top  and  down  to  the  load.  It  is  employed 
to  raise  or  lower  a  weight,  and  is  limited  as  to  height  of  lift  by 


FIG.  490, 


upper  sheave.  Horizontal  motion  is  difficult  but  can  be  obtained 
by  manipulating  guys  with  block  and  tackle.  May  be  moved 
from  place  to  place  by  lifting  bodily  with  a  derrick,  by  sliding 
foot  and  paying  out  or  pulling  in  guy  lines,  or  by  taking  down 
and  setting  it  up  again. 

An  A  frame  is  much  like  a  gin-pole  except  that  mast  is  made 
of  two  inclined  struts  braced  together  and  that  less  guys  are 
needed,  one  being  sufficient.  Methods  of  lifting  and  moving 
are  also  similar. 

Steel  and  wooden  derricks,  Fig.  49^,  guyed  either  by  wire1 
ropes  or  stiff  legs  are  familiar  to  all.  They  are  moved  like  gin- 


FABRICATION  OF  STRUCTURAL  STEEL  121 


FIG.  496  — Derrick  Erecting  85-foot  Plate  Girder  on  Western  Maryland  R.R. 


FIG.  4QC. — Derrick  Car,  American  Bridge  Co.,  Ambridge.  Pa. 


122  ELEMENTS  OF  STRUCTURAL  DESIGN 

poles.  These  not  only  raise  or  lower  the  load,  but  they  can  place 
it  almost  anywhere  within  a  hemisphere  whose  center  is  the 
foot  of  the  mast  (the  upright  piece)  and  whose  radius  is  the 
boom  (the  movable  piece).  This  is  likely  to  be  somewhat 
limited  by  (a)  Lack  of  strength  in  derrick  for  certain  positions 
of  the  load,  (b)  Construction.  For  example,  guys  might  inter- 
fere, (c)  Objects  on  the  ground. 

Derricks  mounted  on  a  car,  that  is,  derrick  cars,  Fig.  49^, 
are  very  efficient  machines.  They  are  commonly  provided  with 
a  hoisting  engine,  air  compressors,  and  full  sets  of  tools.  The 
mast  is  designed  to  collapse  and  the  boom  if  a  long  one  is  made 
telescopic;  hence  they  may  be  shipped  from  shop  to  site  like  an 
ordinary  freight  car.  It  can  move  slowly  under  its  own  power 

even  with  load.     Its  field  of  action 
is    a    semi-cylinder  whose  axis  is   a 
line  through  the  foot  of  the  mast  and 
parallel  to  the  track,  and  whose  radius 
is  the  boom.     When  raising  loads  at 
one  side,  the  other  may  be  prevented 
FIG.  49rf.-Use  of  Auxiliary       from  ^P1^  bY  loading    an  auxiliary 
Boom.  boom,    Fig.    49^,    by    fastening    one 

wheel  to  track,  or  by  "  outriggers." 

The  latter  are  beams  temporarily  bolted  transversely  to  the 
car  with  ends  supported,  loaded,  or  fastened,  to  counterbalance 
the  eccentric  load. 

A  gallows  frame  is  shown  in  Fig.  490.  It  is  guyed  at  the  top 
and  supported  at  the  bottom.  A  limited  amount  of  motion 
may  be  secured  by  manipulating  guys  or  by  varying  pulls  on 
the  two  ropes  which  support  the  load.  In  the  main,  however, 
its  office  is  to  raise  or  lower  an  object. 

Travelers  are  very  common  in  bridge  work.  There  are  three 
types:  the  ordinary  traveler,  the  cantilever  traveler,  and  the 
creeper. 

The  former,  Fig.  49/,  consists  of  several  gallows  frames 
braced  together  so  as  to  be  independent  of  guying.  Sheaves 
at  the  top  provide  necessary  number  of  hoists,  while  wheels 
on  the  bottom  allow  of  longitudinal  motion.  It  can  carry  a  load 
between  any  two  points  within  its  limits.  The  inside  lines  must 
clear  the  truss  which  it  is  proposed  to  erect. 


FABRICATION  OF  STRUCTURAL  STEEL 


123 


FIG.  4ge. — Unloading  Plate  Girders  by  Gallows  Frame. 


FIG.  4c/. — Ordinary  Traveler,  American  Bridge  Co.,  Ambridge,  Pa. 


124 


ELEMENTS  OF  STRUCTURAL  DESIGN 


A  cantilever  traveler,  Fig.  49^,  is  one  which  overhangs.  Its 
essential  elements  are  two  projecting  trusses  well  braced  together 
and  mounted  on  wheels,  with  sheaves  at  one  end  and  engine 
and  counterbalancing  weight  at  the  other. 

A  creeper  is  shown  in  Fig.  49/2.  It  is  a  small  derrick,  mounted 
on  wheels  which  run  on  the  top  chord  of  the  truss. 

There  is  a  great  deal  of  variety  in  the  design  of  these  erec- 
tion tools,  and  capacity  and  measurements  differ  widely.  Space 


FIG.  4Qg. — Cantilever  Traveler,  American  Bridge  Co.,  Ambridge,  Pa. 

does  not  admit  our  taking  up  the  subject  of  design  of  even  the 
framed  structures.  In  general,  these  may  be  made  of  either 
wood  or  steel.  Follow  conventional  methods  and  use  customary 
allowable  values  for  highway  bridges.  (Vol.  II.)  Special 
care  must  be  taken  to  get  maximum  stresses  under  the  varied 
conditions  met  in  service. 

There  is  even  more  variety  m  the  situation  of  the  site  and 
in  the  ingenuity  displayed  in  overcoming  obstacles  of  various 
sorts.  We  shall  attempt,  however,  to  give  only  common  repre- 
sentative methods. 


FABRICATION  OF  STRUCTURAL  STEEL 


125 


Three  factors  are  of  very  great  importance : 

(1)  If  the  site  can  be  reached  by  rail  or  navigable  waters, 
it  may  be  termed  accessible.     Otherwise,  it  must  be  shipped  in 
small  sections. 

(2)  If  the  traffic  must  be  maintained  except  for  some  inter- 
ruptions of  a  few  hours  each,  it  might  be  designated  continuous 
traffic;    such  are  the  difficulties  attending  construction  of  this 
sort  that  it  frequently  pays,  particularly  with  highway  bridges, 


FIG.  4gh. — Creeper  Traveler  Erecting  Cantilever  Bridge  at  Beaver,  Pa. 
Taken  from  A.  R.  Raymer's  paper  on  the  "Pittsburgh  and  Lake  Erie 
Railroad  Cantilever  Bridge  over  the  Ohio  River  at  Beaver,  Pa.," 
in  Vol.  LXXIII,  Trans.  A.S.C.E.,  opp.  p.  156. 

to  build  a  temporary  structure  near  by  for  use  during  erec- 
tion of  bridge.  It  may  then  be  treated  as  a  case  of  interrupted 
traffic. 

(3)  Delivery  of  material.  It  may  be  brought  onto  tracks 
running  over  structure  which  it  will  replace,  or  alongside^  under- 
neath, or  at  one  end  of  final  location. 


126  ELEMENTS  OF  STRUCTURAL  DESIGN 


ERECTION   OF   PLATE    GIRDERS  * 

There  are  five  methods,  the  first  three  for  new  structures 
or  interrupted  traffic,  the  fourth  and  fifth  for  continuous  traffic. 

(/)  Launching,  Fig.  492',  for  inaccessible  positions  where 
derricks  of  sufficient  capacity  are  not  available  and  where 
material  is  delivered  at  one  end. 

(2)  Girders  may  be  lifted  directly  into  position  (Fig.  490). 

(5)  Tracks,  supported  by  a  temporary  wooden  structure 
called  falsework  are  built  across  proposed  span.  Girders  are 
then  suspended,  one  on  either  side  of  flat  cars,  brought  directly 
over  their  final  position,  and  carefully  lowered. 

(4)  Girders  may  be  brought  to  site  on  flat  cars  and  unloaded 
at  or  near  their  final  position  by  overhead  hoists  supported  by 
falsework. 


FIG.  492*. — Erecting  a  Plate  Girder  by  Launching. 

(5)  Girders  may  be  unloaded  at  one  side  and  shoved  or 
lifted  into  place  as  old  bridge  is  removed,  travel  being  temporarily 
suspended. 

Up  to  the  capacity  of  shipping  facilities  and  erection  tools, 
entire  structure  is  preferably  riveted  up  complete.  The  girders 
themselves  can  be  shipped  in  parts,  but  this  is  very  rare. 

The  girders  may  be  placed  a  little  more  than  their  proper 
distance  apart,  the  intermediate  pieces  put  in  position,  and  then 
the  former  moved  up  to  fit.  A  much  better  way  is  to  make  a 
design  in  which  all  intermediate  pieces  may  be  "  swung  in  " 
with  girders  in  final  position. 

ERECTION   OF  VIADUCTS  f 

These  have  seldom  been  built  to  replace  old  structures. 
Material  is  commonly  unloaded  at  one  end  and  there  reloaded 

*  Engineering  Record,  Vol.  LIX,  p.  494  et  seq. 
t  Ibid,  Vol.  LXI,  p.  429. 


FABRICATION  OF  STRUCTURAL  STEEL  127 

onto  contractor's  cars,  which  deliver  it  to  erector's  gang.  The 
latter  generally  employ  a  derrick  car  or  a  cantilever  traveler. 
Beginning  at  one  abutment,  they  erect  in  order:  the  first  bent, 
the  first  span,  second  bent,  longitudinal  bracing,  second  span, 
third  bent  and  so  on.  Or  the  first  tower,  the  first  span,  the 
second  span,  second  tower,  and  so  forth. 

ERECTION  OF  TRUSS  BRIDGES 

Small  trusses  may  be  shipped  complete  or  riveted  up  at  the 
site  and  handled  like  plate  girders. 

There  are  four  methods  of  erecting  larger  bridges : 

(1)  Falsework,    Fig.    49;'.    This    is    the    usual   way.    The 
falsework  is  composed  of  wooden  trestle  bents.     Posts  and  caps 
are  about  i2//Xi2//  with  3//Xio//  bracing,  resting  upon  piles, 
or,  in  favorable  ground,  mud  sills.     On  top  of  these  bents  are 
supported  the  traveler  and  the  blocking  on  which  the  bridge  is 
placed.     One  proceeding  is  to  begin  at  or  near  center,  erect 
panels  there  on  both  sides,  connecting  up  with  lateral  bracing. 
From  there  trusses  are  erected  towards  fixed  end.     Traveler  is 
next  brought  back  to  center  and  erection  carried  on  towards 
free  end.     Another  method  is  to  erect  floor  system,  fasten  trusses 
to  floorbeams,  in  order  previously  given.     After  the  latter  are 
complete,  blocking  is  removed  and  bridge  settles  onto  its  shoes. 

Other  three  methods  are  employed  where  falsework  would 
be  impracticable  on  account  of  depth  or  rapid  movement  of 
stream. 

(2)  Cantilever.     This  case  is  shown  in  Fig.  49^,  where  the 
two  shore  spans  would  be  erected  by  falsework.     The  center 
span  would  be  built  as  seen  in  the  picture.     Toggle  joints  are 
provided  at  a  and  wedges  at  b.     Trusses  are  built  a  little  high 
and  are  dropped  into  position  to  connect  by  means  of  toggles 
and  wedges.     One  disadvantage  of  this  method  is  the  extra 
material  sometimes  needed  to  carry  the  erection  stresses, 

(3)  In  end  launching,  the  bridge  is  erected  on  shore.     When 
finished,  it  is  pushed  forward  on  rollers,  the  projecting  end 
being  sustained  by  a  float. 

(4)  In  floating,  the  bridge  is  built  on  falsework  carried  by 
scows  sunk  in  the  water.     Latter  is  pumped  out  and  structure 


128 


ELEMENTS   OF  STRUCTURAL  DESIGN 


FIG.  49;'.— Falsework  Supporting  Bridge  during  Erection,  American  Bridge 
Co.,  Ambridge,  Pa, 


FABRICATION  OF  STRUCTURAL  STEEL 


is  towed  to  a  position  just  over  the  final  one,  and  valves  in  the 
bottom  of  scows  are  opened. 

Pins  are  fitted  with  pilot  and  driving  nuts  (Art.  46)  and  driven 
by  means  of  a  wooden  maul  or  a  heavy  suspended  timber. 

When  assembled,  bolts  are  placed  in  the  rivet  holes.  Gen- 
erally but  a  fraction  of  the  open  holes  are  'so  filled.  Enough, 
however,  must  be  inserted  to  carry  the  maximum  stresses  which 
will  occur  before  riveting. 

Rivets  may  be  driven  by  hand  or  a  pneumatic  hammer 
(Art.  37).  The  former  is  now  confined  to  very  small  jobs  or 
places  not  accessible  to  the  latter.  Field  riveting  is  much  more 
expensive  than  shop,  costing  5  to  15  cents  apiece,  or  even  more. 
It  varies  a  great  deal  with  circumstances. 


FIG.  4gk. — Erecting  a  Truss  by  Cantilever  Method. 

The  designer  should  always  consider  erection  and  have  at 
least  one  simple  and  safe  method  in  mind.  Take  the  plans  of 
the  apparatus  which  will  be  used  and  see  how  every  piece  will 
be  placed  in  position.  Bear  in  mind  the  following  principles: 

(a)  Make  field  riveting  a  minimum.     It  is  much  more  expen- 
sive than  shop  yet  not  as  strong. 

(b)  However,  this  should  not  make  pieces  too  large  or  too 
heavy  to  be  readily  handled  or  shipped. 

(c)  Avoid,  if  possible,  groups  of  a  few  rivets  in  inaccessible 
locations.     It  may  often  cost  more  to  build  the  platform  on 
which  the  workmen  stand  than  it  does  to  drive  the  rivets. 

(d)  Consider  how  each  bolt,  pin,   and  field  rivet  will  be 
entered  and  fastened.     For  an  example  of  difficult  driving,  see 
inside  field  rivets  in  Fig.  4Q/. 

(e)  Avoid  entering  joints,  Fig.  ^gm.     This  might  be  obviated 
by  attaching  one  or  both  angles  to  projecting  webs. 

(/)  Allow  ample  clearances  where  it  will  do  no  harm.     Do 


130 


ELEMENTS  OF   STRUCTURAL  DESIGN 


not  attempt  to  get  closer  to  an  interference  than  one-half  inch 
unless  it  will  look  bad  or  weaken  the  structure. 

(g)  Where  a  horizontal  member  frames  into  a  vertical 
surface,  for  example,  connection  of  stringer  and  floorbeam,  an 
angle  on  which  to  rest  the  former  is  a  great  help. 


FIG.  4Q/. 
Interior  Field  Rivets  are  Hard  to  Drive. 


FIG. 
Entering  Joint. 


(H)  Consider  how  anchor  bolts  will  be  placed.  The  best 
method  is  to  set  them  in  holes  drilled  after  erection.  See  that 
enough  room  is  allowed  for  drill  and  hammering  same. 

(i)  Avoid  members  very  much  alike  but  not  exactly  so;  a 
misplacement  may  be  very  expensive. 


CHAPTER  V 
THE   ENGINEERING   DEPARTMENT 

Art.  50.    Specifications  * 

THE  clauses  which  define  a  contract  are  called  the  Speci- 
fications. In  its  completest  sense,  the  word  covers  the  neces- 
sary legal  forms,  statements  of  amounts  and  limits  of  work, 
permissible  materials,  and  rules  of  procedure.  It  is  mainly 
in  the  latter  that  we  are  interested.  These  are  used  not  only 
as  a  part  of  the  agreement,  but  as  a  guide  to  contractor's  engi- 
neers. They  may  specify  simply  the  finished  structure,  leaving 
designer  and  builder  free  to  exercise  their  judgment;  or  they 
may  cover  the  minutest  details  and  processes.  An  intermediate 
course  is  better.  Specifications  should  be  complete,  concise, 
and  clear.  Useless  directions  add  to  the  cost,  while  meager 
allow  inferior  work. 

As  an  example,  we  will  give  a  set  of  specifications  for  railroad 
bridges.  This  will  follow  somewhat  closely  present  (1912) 
average  practice.  Notes  of  occasional  differences  and  other 
comments  will  be  enclosed  in  brackets. 

SAMPLE  SPECIFICATIONS  FOR  RAILROAD  BRIDGES 
(a)  Description 

(i)  Up  to  30  feet.     Rolled  I  beams. 

PREFERRED        30  to  100  feet.    Plate  girders. 
TYPES  100  to  175  feet.     Riveted  Trusses. 

Above  175  feet.     Pin-connected  trusses. 
Deck  bridges  shall  be  used  where  conditions 
permit. 

*  See  Cooper's  1906  Specifications  for  Railway  Bridges;  Ostrup's  Standard 
Specifications. 

131 


132 


ELEMENTS  OF  STRUCTURAL  DESIGN 


PREFERRED 
DEPTH 


0) 

STRINGER 
SPACING 

(4) 

SPACING  OF 

GIRDERS  AND 

TRUSSES 


Depth    shall    not    be    less    than    following 

amounts : 

Plate  girders,  one-tenth  span. 
Trusses,  one-sixth  span. 

Stringer  spacing  shall  be  6  feet  6  inches 
center  to  center,  except  for  curves  or 
some  other  special  reason. 

Center  to  center  spacing  shall  be  as  follows: 
Deck  girders,  one-twelfth  span  but  not  less 

than  6  feet  6  inches. 
Through  girders  to  suit  clearances. 
Trusses,  not  less  than  one-twelfth  span. 


/ 

.     w-o" 

\ 

s 

/ 

C7-O" 

b 
* 

b 

<r 

pf€"  7-0" 

*£ 

3-C 

Z&-0" 

Sir  gle  Tr» 
\ 

k 
/ 

\ 

Double    Track 

*o 

~r 

FIG.  5oa.  FIG.  506. 

Typical  Clearance  Diagrams 


Single  Track. 


Double  Track. 


(5) 
CLEARANCE 

DIAGRAMS 


TIES  AND 
GUARD  TIMBERS 


Bottom  line  in  Figs.  500  and  b  represents 
base  of  rail.  Widths  to  be  increased  to 
give  the  necessary  clearance  on  curves. 

Ties  shall  be  of  white  oak  or  yellow  pine 
eight  inches  wide  and  spaced  as  near  six 
inches  apart  in  the  clear  as  is  practical. 
Make  depth  one-tenth  the  span  but  never 
less  than  eight  inches.  Minimum  notch 
over  supports,  one-half  inch.  Fasten  every 
third  tie  to  stringer  or, girder  by  f"  hook 
bolts.  Guard  timbers  to  be  eight  inches 
wide  and  six  deep  notched  to  4"  over  ties 
and  fastened  by  f"  bolts  to  every  third 
tie. 


THE  ENGINEERING  DEPARTMENT 


133 


w 

DEAD 
LOADS 

w 

OWN 

WEIGHT 


0) 

LIVE 
LOAD 


oooo 


(b)  Loads 

Dead  loads  shall  be  computed  in  all  cases. 
Allow  125  Ibs.  per  ft.  per  track  for  rails. 
Timber  to  be  considered  as  green  and 
estimated  as  given  in  Art.  2.  Assume 
ballast  to  weigh  no  Ibs.  per  cu.ft. 

Stresses  due  to  own  weight  must  be  allowed 
in  the  design. 

[Impact,  which  is  often  included  in  specifi- 
cations, is  covered  by  formula  for  unit 
stresses.] 

The  live  load  per  track  shall  be  taken  as 
Cooper's  E  50,  as  given  in  Fig.  50^.  Weights 
are  in  thousands  of  pounds. 


«*J       <0         ">       *> 

O  O  O  O 


OOOO    o 


3 

O 


Q  O 


5  1C    I  5 


555 


.5  1,5  I  feet 


(4) 

CENTRIFUGAL 
FORCE 


FIG.  5oc.  —  Loading  Cooper's  E  50. 

Centrifugal   force,   F,   shall  be   assumed   to 
act  at  a.  point  6  feet    above  base  of  rail. 
Let  D  =  degree  of  curvature,  PF  =  live  load 
on  bridge,  v  =  velocity  in  feet  per  second. 
(Assume  a  speed  in  miles  per  hour  of  60  —  $D)  . 
F  =  Wv2/gr.     Substituting: 
v  =  (6o—  jZ>)  5  280/3600  feet  per  sec. 
£  =  32.2  ft.  per  sec.  per  sec. 
r  =  (^6o/D)  in  feet. 
We  may  derive  the  following  formula: 


(5) 

TRACTIVE 
FORCE 


A  force  equal  to  one-fifth  the  live  load  on 
the  bridge  shall  be  considered  to  act 
horizontally  along  base  of  rail  in  either 
direction. 

The  wind  shall  be  taken  as  30  Ibs.  per  sq. 


134  ELEMENTS  OF  STRUCTURAL  DESIGN  . 

(6)  ft.  acting  on  structure  and  train  or  50  Ibs. 

WIND  per  sq.ft.  on  former    alone.      Consider  all 

trusses  but  only  one  plate  girder  to  receive 
this  pressure. 

(c)  Allowable  Unit  Stresses  in  Ibs.  per  sq.in. 

Let  us  take  C  to  represent  the  safe  unit 
stress  for  quiescent  tension  equals  9000 
for  soft  steel,  10,000  for  medium  steel,  and 
15,000  for  3  per  cent  nickel  steel.  Let 

x  minimum  stress 
2  maximum  stress' 

R  =  maximum  slenderness  ratio 

unsupported  length 
least  radius  of  gyration* 

Tension  on  net  section,  CM 

(1)  Compression  on  gross  section,  CM(i  —  .oo6R) 
ALLOWABLE        Shear  on  shop  rivets,  pins,  and 

UNIT  gross  section  of  webs,  2CM/$. 

STRESSES          Shear  on  field  rivets  and  bolts,       CM/ 2. 
Bearing  on  shop  rivets  and  pins,  4.CM/$. 
Bearing  on  field  rivets  and  bolts,  CM. 
Bending  on  pins,  1.5  CM 

Other  flexural  stresses,  CM. 

The  fraction  minimum/maximum  shall  be 
considered  as  negative  if  there  is  a  reversal 

(2)  of   stress.     Members   are   to   be   designed 
for  either  (a)   80%  of  maximum  stresses 

COMBINATIONS  due  to  dead,  live,  centrifugal,  tractive,  and 
wind,  or  (b)  the  first  three.  The  larger  of 
these  two  values  must  be  employed. 

(3)  For  wood,  see  Art.  6.    Allowable  stress  per 
OTHER  ALLOW-         lineal  inch  on  medium  steel  rollers  is  300 
ABLE  VALUES  times    diameter    in    inches.     For    bearing 

on  masonry,  300  pounds  per  sq.in. 


THE  ENGINEERING  DEPARTMENT 


135 


(l) 

ACCESSIBILITY 
AND  DRAINAGE 

(2} 

MINIMUM 
THICKNESS 

(?) 

GRIP 

(4) 
SECTION 

DESIGN 


(d)  Design 

Sections  and  details  shall  be  accessible  for 
cleaning,  painting,  and  inspection,  and  shall 
not  retain  water. 

Except  for  fillers  and  lacing  bars,  minimum 
allowable  thickness  of  metal  is  f  inch. 

The  grip  of  the  rivets  shall  not  exceed  5 
times  its  diameter  (Art.  47). 

Avoid  large  sectional  areas  which  receive 
their  stresses  indirectly  [e.g.,  cover  plate 
on  top  chord,  Fig.  50 d,  should  be  kept  as 
thin  as  conditions  permit.  This  is  because 
compression  distributes  itself  unequally, 
giving  the  heaviest  unit  stresses  in  the  webs, 
W,  and  the  least  in  plate,  P.] 


FIG.  $od. — Distribution  of  Stress  in  a  Built-up  Section. 

(5)  If   angles   be   connected   by   one   leg   only, 
ANGLE  its  area  will  be  considered  as  that  leg. 

CONNECTIONS         This  clause  shall  not  operate,  however,  to 
reduce  the  radius  of  gyration. 

(6)  Riveted  tension  members  shall  have  a  net 
NET  AREA  area  at  pin  equal  to  five-fourths  that  in 

AT  PINS  body  of  piece. 

(7)  In  deducting  rivet  holes,  diameter  is  to  be 
NET  taken    as    one-eighth    inch    greater   than 

SECTION  nominal  diameter  of  rivet.     In  staggered 

spacing,  use  actual  area  along  the  zigzag 
line  if  it  will  be  less  than  that  in  one  plane. 

(8)  Counters  shall  be  designed  for   25%  addi- 
COUNTERS  tional  live  load  and  a  25%  increase  in  allow- 
able stresses. 


136 


ELEMENTS  OF  STRUCTURAL  DESIGN 


(p)  Maximum    slenderness    ratio    for    members 

MAXIMUM  carrying  wind  or  tractive  forces  only,  125; 

LENGTH  for  other  pieces,  100.     If  slenderness  ratio 

COMPRESSION  for  any  part  of  a  compound  column  exceeds 

MEMBERS  that  of  column  as  a  whole,  the  ratio  for  that 

part  shall  be  used.     The  two  compression 

chords  of  truss  or  plate  girder  bridges  shall 

be  similarly  treated  as  a  large  column  with 

wind   bracing   for   lacing.     [Clause   40,   is 

intended   to   eliminate    the   possibility   of 

lower  stresses  by  this  method.] 

(10)  Bending  stresses  due  to  own  weight  in  com- 

TRANSVERSE  pression  members  may  be  neutralized  by 

LOADS  eccentric  arrangement  of  joints  (Art.  56). 

Other    transverse    loads    are    preferably 

avoided  but  must  be  allowed  for  if  they 

occur. 

(n)  Top  flanges  of  beams  and  plate  girder  must 

TOP  FLANGES  have  their  allowable  stress  reduced  by  the 

PLATE  compression  formula  if  unsupported  for  a 

GIRDERS  distance  greater  than   15   times  width  of 

cover  plate. 

(12)  Rivets  in  the  top  flanges  of  deck  plate  girders 
TOP  FLANGE  and  stringers  shall  be  computed  for  result- 

RIVETS  ant  shear  and  vertical  load.     The  heaviest 

wheel  of  the  loading  is  considered  as  dis- 
tributed over  three  feet. 

(13)  In   computing   plate   girders,   web   shall   be 
COMPUTATION          designed  to  carry  its  share  of  the  bending 

OF  PLATE  moment.     Compression  and  tension  flanges 

GIRDERS  shall  be  made  alike,  and  not  less  than  one- 

third  of  flange  area  shall  be  in  angles  and 
side  plates. 

Stiffeners  shall  be  in  pairs.  At  bearings 
and  points  of  concentrated  loading,  they 
shall  have  sufficient  capacity  to  carry  the 
load  as  a  column.  If  thickness  of  web  is 


THE  ENGINEERING  DEPARTMENT 


137 


(14)  more  than  one-fiftieth  of  the  depth,  other 
STTFFENERS  stiffeners  may  be  omitted.       If  not,  they 

shall  be  spaced  one-half  to  one-third  depth 
apart  at  ends  and  depth  apart  at  the  middle. 
At  intermediate  points,  use  a  proportionate 
spacing. 

Complete  upper,  lower,  and  sway  lateral 
systems  shall  be  provided  where  possible; 
under  other  circumstances  as  in  through 

(15)  structures,  bracing  will  be  designed  to  be  of 
BRACING  the  necessary  strength  and  as  efficient  as 

practicable.  Solid  floor  shall  be  considered 
as  a  lateral  system  in  its  own  plane.  Struts 
located  at  or  near  shoes  shall  be  capable 
of  resisting  temperature  stresses. 

0)  Details 

Rivets  may  be  },  f  or  i  inch  diameter,  d. 
Let  /  equal  thickness  of  thinnest  outside 

(1)  plate,  then: 

RIVET  Max.  edge  distance  =  8/, 

SPACING  ' '      spacing  =  i6/,  but  not  more 

than  6  inches. 
Min.  edge  distance  =  i. 5 J, 
"     spacing  =^d. 

When  staggered,  spacing  is  the  shortest 
distance  center  to  center  of  rivets.  Above 
rules  for  maximum  do  not  apply  to  two 
angles  riveted  together. 

(2)  Number  of  field  rivets  shall  be  kept  as  low 
FIELD  RIVETS          as  possible.     (Art.  49.) 

A    latticed    compression    member    shall    be 

(j)  figured  for  a  uniform  transverse  load  equal 

LATTICED  to   1/30  strength  of  member  as  a  short 

COMPRESSION          strut.     (Art.   56.)     It  shall  have  as  near 

MEMBERS  ends  as  practical,  batten  plates  not  shorter 

than  greatest  width  of  member,  and  not 


138 


ELEMENTS  OF  STRUCTURAL  DESIGN 


thinner  than  1/50  of  transverse  distance 
between  rivets.  Longitudinal  spacing  on 
batten  plates  shall  not  exceed  4^. 

(4)  The    transverse    distance    between    rows    of 
RIVETED  rivets  in  plate  shall  not  exceed  40/5   longi- 

COMPRESSION  tudinally,  the  space  will  not  be  more  than 

MEMBERS  4^  for  a  distance  from  ends  equal  to  twice 

the  greatest  width  of  the  member. 

(5)  All  joints  must  be  fully  spliced  except  the 
SPLICES  milled  ends  of  short  well-braced  columns. 

For  the  latter  use  two  rows  of  rivets  on 
each  side  of  joint  on  all  four  faces. 

(6)  Verticals  which  carry  tension  shall  be  designed 
RIGID  as    stiff    members.     In    riveted    trusses, 

MEMBERS  tension    members    must    be    battened    or 

latticed.  Connection  of  floorbeam  and 
trusses  must  be  rigid. 

(7)  To  provide  a  camber  for  trusses,  make  top 
CAMBER  chord  longer  than  bottom  by  \  inch  in 

every  10  feet. 

(8)  Provision   for  an  expansion  of  J  inch  in  10 
SHOES  feet  shall  be  made.     Spans  over  75  feet 

must  have  hinged  shoes,  fixed  at  one  end 
and  rollers  at  the  other.  The  diameter 
of  these  rollers  in  inches  shall  exceed  by 
3  the  span  in  feet  divided  by  100.  Rollers 
and  pins  shall  be  made  of  medium  steel. 


(/)  Workmanship 

(1)  Workmanship   shall   be   first-class   in   every 

respect. 

(2)  Where  material  is  thicker  than  -  diameter  of 
PUNCHING  AND         rivet,  hole  must  be  drilled  from  the  solid. 

REAMING  All  other  holes  for  shop  and  field  rivets 

shall  be  punched  |  inch  smaller  than  nomi- 


THE  ENGINEERING  DEPARTMENT 


139 


0) 

RIVETS 

(4) 
TURNED  BOLTS 

(5) 
SHEARED  EDGES 


STIFFENERS 

-  (7) 
UPSET 

ENDS 


(8) 

PIN 

HOLES 


ADJUSTABLE 
MEMBERS 


nal   diameter   and   reamed   to    1/16   inch 
larger  after  assembly. 

All  rivets  must  be  tight,  completely  All  the 
hole,  and  have  full  round  concentric  heads. 

When  replacing  rivets,  bolts  must  be  turned 
to  fit. 

Sheared  edges  of  medium  steel  plate  over  f 
inch  thick  shall  be  planed. 

Stiffeners  and  their  fillers  must  be  fitted  to 
flange  angles. 

Welds  are  forbidden.  Eyebars  and  upset 
ends  shall  be  annealed.  Strength  of  either 
of  the  last  two  must  exceed  that  of  body 
of  bar. 

Holes  shall  be  placed  in  center  of  member 
unless  otherwise  shown;  clearance  of  pin 
in  hole  shall  be  1/50  inch  if  diameter  be 
less  than  5  inches;  1/32  inch,  if  more. 
Distance  between  holes  shall  not  vary 
more  than  one-twenty-thousandth  from 
true  length. 

Adjustable  members  shall  be  avoided  where 
possible.  When  necessary,  use  turn- 
buckles. 


(g)  Painting  and  Erection 

(i)  All  steel  before  leaving  shop  shall  be  cleaned 

SHOP  of  rust  and  given  one  coat  of  paint.     Sur- 

PAINT  faces  which  will  be  in  contact  afterwards, 

must  be  painted  before  assembly.     Pins, 

pin  holes,  screw  threads  and  rollers  shall 

be  coated  with  white  lead  and  tallow  before 

shipping. 


140 


ELEMENTS  OF  STRUCTURAL  DESIGN 


Parts    not    accessible    after    erection    shall 

(2)  receive  one  coat  at  shop  and  one  at  site 

FIELD  before  erection.     Other  parts  shall  receive 

PAINT  two  coats  in  their  final  position.     Painting 

shall  not  be  done  in  wet  or  freezing  weather. 

(5)  Pilot    and   driving   nuts   must   be   used   in 

PINS  driving  pins. 

[For  the  sake  of  conciseness,  we  have  omitted 
paints  and  other  materials.  In  specifying 
them,  use,  if  possible,  some  standard 
specifications.] 


Art.  51.    Problem  of  Design 

The  site  of  the  proposed  structure  should  first  be  surveyed 
and  a  map  prepared.     The  object  of  this  is: 

(1)  To  locate  the  structure  in  the  most  economical  position. 

(2)  To  enable  its  details  to  be  specified  in  advance, 
(j)  To  determine  quantities  and  estimate  cost. 

Property  lines,  buildings,  contours,  soundings,  and  borings 
should  be  taken.     The  latter  ought  to  extend  to  rock,  and  if 

there  is  doubt  as  to  its  integ- 
rity, should  be  examined  by 
the  diamond  drill,  which  with- 
draws a  core  for  examination. 
Consider  every  possible  loca- 
tion, a  few  rough  measurements 
often  showing  the  impractica- 
bility of  some  designs.  It 
may  be  necessary  to  place  the 
structure  at  a  particular  spot, 
but  it  is  even  then  better  to 
make  the  survey  for  reasons 

FIG.  51.— Alternative  Routes  for          (2)  an<^  (j)j 

Railroad  Location.  To   indicate  the   necessity 

for    thorough  information,  let 

us  take  the  case  shown  in  Fig.  51.     The  problem  is  to  locate  a 
railroad  between  the  two  towns  and  design  the  necessary  struc- 


THE  ENGINEERING  DEPARTMENT  141 

tures.  The  cost  of  operating  would  be  least  if  alinement  and 
grade  were  straight  from  one  town  to  the  other.  But  first  cost 
would  probably  be  lessened  by: 

(ai)  Going  farther  up  the  valley  and  using  a  shorter  bridge 
but  a  longer  line. 

(#2)  Cutting  deeper  into  the  hill  at  the  towns,  and  so  lessen- 
ing depth  in  valley. 

(as)  Lowering  grade  in  valley. 

Various  modifications  and  combinations  of  these  should  be 
worked  out. 

(bi)  Consider  now  that  alinement  and  grade  for  railroad  are 
chosen — shall  we  use  a  viaduct  or  a  bridge  with  abutments  or 
fill  all  the  way  across,  leaving  only  a  culvert?  In  the  first  two 
cases,  where  will  it  be  economical  to  stop  the  fill  and  begin  the 
viaduct  or  bridge? 

(62)  Suppose  location  and  ends  of  fill  to  be  settled,  shall  we 
use  timber,  steel,  stone,  concrete,  reinforced  concrete,  or  com- 
binations of  these? 

(63)  After  material  is  selected,  what  shall  be  the  spans? 
Shall  they  be  uniform,  making  superstructures  alike,  or  shall 
they  increase  as  valley  becomes  deeper?    We  might  use  one  very 
long  span  or  many  very  short  ones,  but  obviously  the  former 
would  result  in  an  exceedingly  expensive  bridge,  while  the  latter 
would  give  many  abutments  and  piers>  thus  increasing  cost. 

(64)  Closely  allied  to  this  is  the  type  of  bridge.    Considering 
now  only  a  steel  bridge,  shall  it  be  arch,  suspension,  cantilever, 
or  simple  truss?     Shall  we  use  the  through  or  the  deck  structure? 

(65)  Type  having  been  determined  upon,  what  should  be  the 
depth  and  what  the  panel  length? 

(bo)  Coming  down  now  to  the  design  of  the  members  of  the 
truss  and  taking  the  individual  pieces,  what  combinations  of 
structural  shapes  will  carry  the  stresses  economically  and  make 
easy  and  efficient  joints? 

(67)  Even  in  the  details  of  the  latter,  there  are  various  types 
each  having  its  own  advantages. 

In  this  example,  we  have  indicated  only  a  few  of  the  questions 
which  are  interwoven  with  the  problem  of  design.  Some,  it 
will  be  noticed,  are  a  little  outside  the  province  of  the  structural 
engineer.  We  will  answer  them  all  in  the  same  way: 


142  ELEMENTS  OF  STRUCTURAL  DESIGN 

CHOOSE  THE  MOST  ECONOMICAL  DESIGN  WHICH  GIVES  THE 
REQUIRED  DEGREE  OF  SAFETY. 

For  elements  of  cost,  see  Art.  27.  (#1),  (#2),  and  (03)  belong 
to  Railroad  Engineering.  In  (7>i),  speaking  roughly,  we  would 
stop  fill  at  a  depth  where  cost  of  fill  per  lineal  foot  became 
greater  than  cost  of  bridge.  But  it  must  be  remembered  that 
maintenance  charges  are  much  lower  for  a  properly  built  fill 
and  its  sinking  fund  would  be  zero.  These  operate  therefore  to 
increase  depth  where  fill  stops. 

(£2)  Timber  is  cheaper  in  its  first  cost  but  maintenance  and 
renewal  charges  are  higher.  Properly  built  masonry  bridges 
.have  neither  maintenance  nor  sinking  fund  charges,  but  their 
first  cost  is  high,  they  cannot  be  used  for  long  spans,  and  they 
are  ill  suited  to  foundations  on  compressible  soils  such  as  are 
quite  common.  We  shall  confine  ourselves  to  steel  structures 
in  the  remainder  of  this  treatise. 

The  rest  of  our  work  will  be  taken  up  in  discussing  the 
remaining  points  for  different  structures.  Special  reference 
may  be  made  to  Art.  52  for  (63)  and  (5s);  Arts.  54,  55,  and  56, 
(to);  Arts.  58,  59,60,  (67). 

Very  often  considerations  other  than  economical  ones  will 
govern.  Such,  for  instance,  are  the  architectural  appearance 
or  legal  difficulties.  All  possible  alternatives,  however,  must 
be  very  carefully  investigated.  Do  not  make  arbitrary  decisions 
but  prepare  estimates  of  cost  until  certain  that  the  most  desir- 
able scheme  has  been  found. 

Plans  are  better  if  completed  before  construction  is  begun, 
although  it  is  true  that  many  changes  will  have  to  be  made 
as  the  work  progresses.  Estimates  of  cost  can  then  be  finished 
with  much  more  ease  and  economy.  These  do  not  have  that 
uncertainty  which  is  likely  to  mean  high  bids  from  responsible 
contractors. 

To  estimate  the  cost,  quantities  are  computed  from  the 
preliminary  plans.  Since  these  will  probably  be  changed  more 
or  less  in  actual  construction,  rules  which  are  only  approximately 
correct  are  often  employed.  Each  quantity  multiplied  by  its 
estimated  price  gives  the  total  amount  to  which  something  like 
ten  per  cent  should  be  added  for  contractor's  profit. 

Often  the  designing  and  estimating  for  the  steel  work  is 


THE  ENGINEERING  DEPARTMENT  143 

done  by  the  fabricating  company.  However,  if  there  is  no 
competition,  the  purchaser  will  pay  dearly  for  advice  obtained 
in  that  way.  If  competitive  designs  are  requested,  the  buyer 
really  pays  for  them  all.  Structural  steel  is  let  either  by  the 
pound  or  the  lump  sum,  the  latter  signifying  a  fixed  amount 
for  the  whole  job.  In  the  former  case,  the  contractor  may  try 
to  use  as  heavy  material  as  he  can;  in  the  latter,  as  light  as 
possible,  that  is,  he  tries  to  "  skin  "  the  bridge.  To  prevent 
this,  plans  and  specifications  should  be  thorough  and  explicit, 
simply  allowing  the  necessary  latitude  for  varying  shop  practice. 
Best  method  is  then  as  follows:  The  general  design  and 
sizes  of  all  material  are  determined  by  purchaser's  engineer. 
Plans  and  specifications  are  next  prepared  and  sent  to"prospect- 
ive  bidders.  The  latter  take  off  the  quantities  in  the  estimating 
room  and  make  their  own  estimate  of  cost,  usually  on  the  basis 
of  structure  ready  for  traffic.  This  with  an  allowance  for  profit 
is  submitted  as  a  bid.  The  lowest  responsible  bidder  is  then 
given  the  job. 

Art.  52.    Economical  Relations 

Given  a  structure  of  a  certain  type,  there  are  relations  between 
measurements  which  produce  the  most  economical  design. 

(/)  As  an  example,  let  us  take  the  case  of  a  plate  girder  of 
a  given  span  and  loading.  The  weight  of  the  web  and  its 
fittings  is  about  constant  per  square  foot.  Letting  h  represent 
depth,  we  may  then  say: 

Total  weight  of  web  =  Cih. 

Using  approximate  method  of  computation,  Art.  54,  the  area 
of  the  flange  and  hence  its  weight  will  vary  inversely  as  the 
depth,  or 

Total  weight  of  both  flanges  =  Cz/h  -, 

K  -        - 

Total  weight  of  girder  =  Cih+C2/h.  =  W 

Placing  first  derivative  equal  to  zero  to  obtain  value  of  h 
which  renders  weight  a  minimum  : 


or 


144  ELEMENTS  OF  STRUCTURAL  DESIGN 

Hence,  make  depth  of  girder  such  that  weight  of  both  flanges 
equals  that  of  the  web  and  its  fittings. 

The  above  proof  assumes,  as  often  happens,  that  minimum 
thickness  of  web  suffices.  Where  it  does  not,  W  =  Ci  +  C2//f. 
Hence,  for  the  latter  case,  increase  depth  as  much  as  practical 
or  until  minimum  thickness  of  web  is  reached. 

(2)  Let  a  river  crossing  have  x  spans  of  length  L/x  and 
suppose  the  foundations  to  be  the  same  throughout  its  length. 
The  cost  of  the  steelwork  for  the  floor  will  be  constant  and  we 
will  call  it  F.  That  of  trusses  will  vary  as  square  of  span  and 
we  will  represent  it  by  CxL2/x2  =  CL2/x.  The  cost  of  each 
pier  will  be  about  the  same  whatever  the  span  and  we  will  call 
each  P  and  total  amount  Px. 

The  entire  structure  then  has  a  cost: 

E=F+CL2/x+Px, 

=  o    or    Px  =  CL2/x. 


Hence  cost  of  piers  equals  that  for  trusses  in  an  economical 
structure. 

(3)  For  the  comparison  of  trusses,  we  may  find  the  sum  of 
the  products  of  maximum  stress  in  each  member  by  its  length. 
That  truss  for  which  this  sum  is  a  minimum  is  the  most  econom- 
ical. However,  this  method  does  not  take  into  account  one  very 
important  fact:  that  for  the  same  stress,  steel  compression 
members  are  a  great  deal  more  expensive  than  tension  members. 
The  following  example  will  explain  not  only  how  this  may  be 
allowed  for  but  also  show  method  of  applying  calculus. 

Everything  in  kips  and  inches. 

Allowable  unit  stresses  : 


Tension  =  8.0, 

Compression  =  8.o(  i ) , 

\       1 60  p/ 


A 

if  p  =  — ,  then 
4 


Compression  =  8  .o  (  i ) . 

40^47 


THE  ENGINEERING  DEPARTMENT 


145 


Let  51  =  allowable  unit  stress  in  tension  or  pure  compression; 

T  =  total  stress  ;  length  of  member  =  L. 
Then  volume  in  tension  =  TL/S, 

Then  volume  in  compression  =AL  =  TL/S\  i  --  -) 

\      40  A/ 


or 


or 


=  T/S+L/40y 


FIG.  52. — Economical  Height,  Pratt  Truss. 


Mem- 
ber. 

Total  Stress, 
T 

Length, 

Volume  of  I, 
V 

Num- 
ber. 

Total  Volume. 

6W(p*+h^ 

f/>2_L/,2H 

6W  p*+h*    p*+h* 

I2tF/>2+A2       />2  +  &2 

2 

h 

-8wf 

h 

+6WP 

\p  -\-n  )3 

P 
•h 

S         h           40 

'  Wpt+Zl 
Sh  P  +4o 

6Wp* 

2 

S        h            20 
2™P,+P1 

Sh  P  +20 

Wp* 

4 
5 

h 

+3W 

-W 

2W(P*+W 

P 
h 
h 

fA2_L£21\i 

Sh 

$Wh 
S 

Wh    hz 
S  +40 

oW 

(h*  Li2^ 

4 

2 

I 

24  Sh 

6Wh 
S 

K 

^      (A2  1  A2^ 

h 

\p  -\-n  )3 

Sh(P+h) 
Total  

5A(P 
56PT^        Wh     p*    3A2 

_i_2?  -j  

• 

Sh         6  S  Tio^  40 

SF 


Sh 


= 

2   '      S       20      ' 


146  ELEMENTS   OF  STRUCTURAL  DESIGN 


or  2>Sh3  +46oWh2  =  1  1  2oWp2. 

Here  TF  =  iodead.     S  =  8.o.     ^  =  240. 

Substituting,  h  =  247  =  20'  —  7". 

For  doubtful  or  irregular  cases  where  above  methods  cannot 
be  used,  make  several  designs  and  estimate  quantities  and 
costs.  The  greater  the  magnitude  of  the  work,  the  more  need 
for  time.  Do  not  spend  a  large  amount  of  money  upon  a  small 
or  typical  structure  but  follow  current  practice.  A  saving  of 
$50  in  material  at  a  cost  of  $100  in  drawing  room  is  poor  engi- 
neering. 

There  are  very  many  practical  points  interwoven  with  this 
question.  For  example,  the  most  economical  length  of  an  I 
beam  span  will  be  one  where  a  standard  depth  of  the  minimum 
weight  is  just  loaded  to  its  full  capacity.  Again  in  a  viaduct  of 
varying  depth,  span  should  change  to  correspond  as  indicated 
in  (2)  of  this  article.  However,  spans  thus  determined  might 
be  too  long  to  be  easily  erected,  and  a  great  deal  of  time  might 
be  saved  in  designing,  detailing,  and  fabricating,  if  they  were 
made  alike  or  perhaps  in  two  or  three  different  lengths, 

Art.  53.    Estimating 

While,  strictly  speaking,  this  includes  only  the  approximate 
determination  of  weights  and  cost,  the  estimating  room  of  a 
structural  company  has  following  functions  to  perform  : 

(1)  To  determine  what  kind  of  a  structure  shall  be  used 
in  a  given  location  and  what  its  general  dimensions  shall  be. 
(Arts.  51  and  52). 

(2)  To  specify  loads  and  unit  stresses.     (Art.  50). 

(3)  To  compute  total  stresses  in  various  parts  of  the  struc- 
ture. 

(4)  To  design  these  members.     (Arts.  54,  55,  56). 

(5)  To  outline  in  a  rough  way  the  details. 

(6)  To  estimate  weight  and  cost  of  the  different  items. 

(i),  (2),  and  (j)  ought  to  be  done  by  purchaser's  engineer, 
and  (4)  and  (5)  are  often  so  handled. 

An  estimator  must  hence  be  thoroughly  posted  on  both 


THE  ENGINEERING  DEPARTMENT  147 

theoretical  and  practical  work.  His  is  the  highest  position  in  the 
engineering  department  which  does  not  require  the  handling 
of  men. 

(6)  is  best  done  by  writing  a  rough  bill  of  material  and  thus 
getting  weight  and  cost.  This,  carefully  made,  is  accurate  and 
detailer  can  keep  his  work  close  to  the  estimated  figures.  How- 
ever, it  is  usually  done  in  a  hurry,  and  there  is  seldom  time  for 
anything  but  the  roughest  sort  of  drawings.  Hence  the  esti- 
mator tends  to  forget  certain  parts  and  therefore  underestimates. 

Time  is  often  too  short  even  for  the  above.  Then  the 
section  may  be  considered  as  running  from  joint  to  joint  and 
either  a  fixed  length,  a  fixed  amount,  or  a  percentage  then 
added.  This  varies  a  great  deal  with  so  many  conditions  that 
we  cannot  attempt  to  give  values  here.  It  should  be  figured 
out  for  typical  members  or  abstracted  from  similar  cases.  Weight 
of  rivet  heads  are  often  added  as  a  percentage  and  this  too  is 
quite  changeable. 

An  even  more  approximate  method  is  to  use  formulae  express- 
ing some  relation  between  weight  and  the  dimensions  of  the 
structure.  Such  is: 

W = o.  $as(i  +o.  1 5$. , 

as  already  given  for  wooden  trusses  in  Art.  28.  Or  we  may 
estimate  from  diagrams  plotted  from  actual  weights  of  com- 
pleted structures. 

Allowance  should  be  made  for  waste  and  .for  possible  varia- 
tion of  weight  in  rolling.  Where  work  is  to  be  let  by  the  pound 
price,  only  relative  amounts  are  necessary  and  accuracy  is  not 
so  essential.  The  cost  on  each  different  class  of  raw  material 
is  determined  by  consulting  price  card  of  steel  company.  For 
other  items,  a  number  of  very  important  points  arise: 

(a)  Are  members  unlike  one  another  or  may  they  be  made 
the  same?     The  latter  lowers  cost  everywhere  and  especially 
in  pattern,  templet,  and  drawing  room. 

(b)  Is  the  structure  skew  or  square?     The  former  involves 
a  great  deal  of  expensive  blacksmi thing,  and  notably  increases 
labor  in  detailing  and  fabricating. 

(c)  Are  the  specifications  unusually  strict?     Many  desirable 
features  are  costly,  for  example,  sub-punching  and  reaming. 


148  ELEMENTS  OF  STRUCTURAL  DESIGN 

(d)  Are  erection  conditions  favorable?    Is  the  site  handy 
to   the   railroad?    Will   unusual   equipment   be   required?     Is 
there  danger  of  the  structure  being  carried  away  by  floods  or 
ice? 

(e)  Is  enough  time  allowed  for  economical  work? 

Very  rough  average  cost  for  erected  steel  is  about  as  follows — 
1912. 

Cents  per  Ib. 

Material .* 1.20 

Engineering 0.15 

Templet 0.08 

Shop 0.80 

Erection 0.60 

General  expenses 0.17 

Transportation Variable 

Or  3.0  cents  per  pound  plus  transportation. 

The  pieces  of  which  a  structure  may  be  composed  are  beams, 
tension  members,  and  columns. 

Art.  54.    Design  of  Beams 

Beams  may  be  made  of  angles,  I  beams,  channels,  T  beams 
zee  bars,  rails,  trough  sections,  or  built-up  members. 

Plates  are  sometimes  used  for  flooring.  As  an  example  of 
their  use,  let  it  be  required  to  find  allowable  span  of  f  inch 
medium  steel  plate  when  subjected  to  a  load  of  500  Ibs.  per  sq. 
ft.,  using  specifications  of  Art.  50.  This  is  a  uniformly  loaded 
beam.  Considering  a  strip  one  foot  wide:  Total  load  =  (500+ 
15)712=43  Ibs.  per  lin.in. 

M=Sbh2/6,    5  =  io,ooo.     6  =  12,     A  =  |. 
=  10,000- 12- 97(64- 6)  =  2810  Ib.-in. 
/  =  (8M/w)*  =  (8  •  2810/43)*  =  23  inches  allowable  span. 

Although  probably  continuous,  American  practice  is  to 
regard  it  as  a  simple  span.  The  minimum  is  so  small  that  it 
is  considered  as  zero  in  formula  for  allowable  stress. 

Angles,  zee  bars,  and  channels  are  not  symmetrical  about 
center  line.  There  is  danger  that  the  load  may  be  applied 


THE  ENGINEERING  DEPARTMENT 


149 


eccentrically  and  thus  cause  an  injurious  twisting,  Fig.  540. 
Nevertheless,  they  are  used  quite  a  bit  in  situations  where 
their  form  renders  them  more  convenient.  As  an  example,  let 
it  be  required  to  design  a  soft  steel  angle  to  carry  a  load  of  300 
Ibs.  per  lin.ft.  for  a  span  of  8  feet.  Allowable  stress  in  flexure, 
16,000;  shear,  12,000,  both  in  pounds  per  sq.in. 

Maximum  moment  =  Wl/8  =  2400  •  96/8  =  28,800  in.-lbs. 
I/c  =  M/S  =  28,800/16,000  =  1.8. 

Use  5"X3"X5/i6"  weighing  8.2  Ibs.  per  lin.ft.  with  long  leg 
parallel  to  the  load.  Testing  for  shear: 

S  =V2az/bI*  =  1200 -i. 66 -3.32- 0.317(0.31  -6.26)  =  1050  Ibs. 
per  sq.in.,  max.  shearing  stress.     0.  K. 


i 


I 


FIG.  54<z. — Application  of  Load  to  a 
Channel  Used  as  a  Beam. 


FIG.  546. 
Separator. 


A  symmetrical  section  could  be  made  out  of  this  by  fastening 
together  two  angles  whose  joint  capacity  would  be  600  Ibs.  per 
lin.ft.  However,  an  I-beam  would  be  more  economical  as  the 
angles  would  have  to  be  riveted  together  and  the  former  would 
weigh  less. 

Thus  to  design  an  I-beam  equivalent  to  the  two  angles 
whose  combined  weight  is  16.4  Ibs.  per  lin.ft.,  we  look  for  one 
with  a  section  modulus  equal  to  or  greater  than  3.6.  We  might 
use  a  4"  at  10.5  Ibs.  or  a  5"  at  9.75  Ibs.  Assuming  as  usual 
that  shear  is  uniformly  distributed  over  the  web,  the  shearing 
unit  stresses  on  gross  area  are  24007(4-0.41)  or  24007(5-0.21)  = 
1460  or  2280  Ibs.  per  sq.in.  They  are  both  O.K.  even  allowing 
for  possible  rivet  holes.  It  will  be  noted  that  while  the  5"  beam 
has  less  weight  it  is  not  quite  J"  thick.  It  is  likely,  therefore, 

*  Merriman's  "  Mechanics  of  Materials,"  Art.  108. 


150 


ELEMENTS  OF  STRUCTURAL  DESIGN 


to  lack  stiffness  and  has  less  resistance  to  corrosion.     Either 
would  effect  a  marked  saving  in  weight. 

Two  I-beams  may  be  used  as  a  single  beam.  They  should  be 
united  by  bolts  which  pass  through  separators,  Fig.  546.  The 
idea  is  to  stiffen  the  top  flanges  and  make  the  two  act  together. 
Two  I-beams  are  not  as  economical  as  one,  but  they  are  sometimes 
used  where  head  room  is  limited  or  where  one  is  not  sufficient. 
It  should  be  remembered  that  the  Bethlehem  Steel  Co.  is  now 
rolling  some  sections  deeper  than  24  inches  and  also  special 
sections  of  less  depth  which  have  larger  resisting  moments  than 
the  standard.  (Art.  21.)  As  a  measure  of  this  increased 
capacity,  the  following  table  shows  safe  loads  for  spans  of  twenty 
feet;  allowable  fiber  stress,  16,000  Ibs.  per  sq.in. : 


STANDARD  SECTIONS. 

BETHLEHEM  SECTIONS. 

No. 

Depth. 

Weight 
per  Foot. 
Ibs. 

Total 
Weight 
per  Foot. 
Ibs. 

Capacity. 
Ibs. 

No. 

Depth. 

Weight 
per  Foot. 
Ibs. 

Capacity. 
Ibs. 

3 

24" 

80 

240 

278,400 

I 

30" 

2OO 

325,000 

2 

24" 

80 

1  60 

185,600 

I 

24" 

140 

187,000 

2 

18". 

55 

no 

94,000 

I 

18" 

92 

95,000 

The  common  type  of  a  built-up  beam  is  shown  in  Fig.  54^;. 
The  web  is  usually  kept  away  from  the  back  of  angles  |"  to  \/f. 
Sometimes  it  is  made  flush  and  chipped  or  milled  off.  The  idea 
is  to  prevent  pockets  for  the  accumulation  of  dirt  and  moisture. 
This  makes  a  good  but  expensive  job.  Occasionally  the  web  is 
allowed  to  project.  Such  may  be  the  case  in  the  supporting 
beams  (stringers)  for  a  railroad  bridge  where  it  makes  the  neces- 
sary notching  of  the  ties  (called  dapping)  easy.  This  can  be 
done  only  where  there  is  no  cover  plate.  The  rectangular 
plates  shown  dotted  may  be  added  to  increase  its  strength. 
Ordinarily,  they  do  not  extend  the  entire  length  of  the  girder, 
but  are  cut  off  to  correspond  with  variations  of  the  bending 
moment. 

The  angles  may  have  equal  or  unequal  legs;  in  the  latter 
case,  the  longer  leg  is  placed  horizontally  since  it  is  more  effective 
in  this  way. 


THE  ENGINEERING  DEPARTMENT 


151 


For  heavier  beams,  there  are  a  number  of  arrangements, 
Figs.  54</  and  e  being  representative  types.  Where  a  heavy  load 
is  to  be  borne  and  the  depth  is  limited,  a  box  girder,  Fig.  54/, 
may  be  employed.  Sometimes  more  than  two  webs  are  used. 

Considering  now  built-up  sections,  there  are  two  methods  of 
computation,  the  exact  and  the  approximate.  The  former 
assumes  that  the  stress  varies  as  the  distance  from  the  neutral 
axis,  the  web  as  well  as  the  flange  bearing  its  share  of  the  moment. 
The  latter  supposes  entire  moment  to  be  carried  by  the  flange. 


Florae 


FIG.  54^.  FIG.  546. 

Typical  Beam  Sections. 


FIG.  S4/. 


(a)    Design  of  Web 

In  either  event,  shear  is  considered  to  be  uniformly  distributed 
over  the  web.  This  is  approximately  true.  We  have  the  formula 
for  shearing  unit  stress  in  Ibs.  per  sq.in. 


where  V  =  total  shear  on  vertical  section  in  Ibs.  ; 

2az  =  statical  moment  about  center  of  gravity  of  part  of 
section  above  point  where  shearing  unit  stress  is 
desired  —  computed  in  inches; 
/  =  moment  of  inertia.  about  center  of  gravity  of  entire 

section  in  inches; 
b  =  breadth  at  same  point  in  inches. 

Now  as  we  pass  up  from  center  of  a  beam  shaped  like  a 
plate  girder,  there  is  no  change  in  V,  /,  or  b,  and  there  is  little 
change  in  2az  until  flange  is  reached  when  stress  drops  off  very 


152 


ELEMENTS  OF  STRUCTURAL  DESIGN 


rapidly  as  shown  in  Fig.  54^.  That  is,  as  the  shear  over  the 
web  is  uniform  and  as  there  is  little  on  flange,  we  assume  entire 
amount  to  be  uniformly  distributed  over  web. 


(b)    Exact  Method  of  Finding  Flange  Area 

Taking  up  now  the  exact  method,  we  assume  a  composition 
of  the  flange  which  we  est!mate  to  be  sufficient.  We  then  com- 
pute /  and  c  as  though  it  were  solid  except  for  rivet  holes,  and 
determine  unit  stress  in  Ibs.  per  sq.in.  at  outside  fiber  of  beam 
from  the  formula: 

S  =  Mc/I, 

where M  =  bending  moment  at  section  in  in.  Ibs.; 

c  =  max.  distance  in  inches  from  center  of  gravity  to 
outside  fiber; 

/=*  moment  of  inertia  about  center  of  gravity  in  inches. 
If  S  comes  too  high  or  too  low,  we  revise  and  recompute. 


T 


FIG.  54g. — Distribution  of 
Shear  in  a  Half  Beam. 


FIG.  54h—  Part 
of  a  Solid  Beam. 


FIG.  542*. — Part  of  a  Built 
Beam. 


(c)   Exact  Method  of  Determining  Rivet  Spacing 

In  the  formula,  S  =  V  "Zaz/bl,  if  we  omit  b,  it  represents 
the  total  shear  per  lin.in.  That  is,  if  we  should  cut  an  I  beam 
as  shown  in  Fig.  54^  and  then  load  it,  we  would  find  longitudinal 
motion  along  plane  of  cut.  To  prevent  this  we  would  need  a 
force  for  every  lineal  inch,  equal  to  V2az/I.  This  force,  it 
will  be  noted  by  referring  to  the  proof,  is  equal  to  the  difference 
per  lin.in.  of  total  stresses  in  cut  off  part.  Similarly,  in  a  built- 
up  beam,  the  tendency  of  some  of  the  shapes  to  shear  off  is  given 
by  the  same  formula.  Thus,  in  Fig.  542',  enough  rivets  must 
be  passed  through  the  angles  to  safely  carry  this  force. 


THE  ENGINEERING  DEPARTMENT  153 

If,  as  often  happens,  there  is  a  vertical  load  on  top  or  bottom 
of  the  girder,  the  vertical  stress  per  lineal  inch  must  be  combined 
with  the  horizontal  to  obtain  resultant.  It  is  usual  for  ease 
of  fabrication  to  make  both  flanges  and  their  rivet  spacing  alike, 
hence  only  spacing  on  loaded  chord  need  be  computed. 

(d)    Approximate  Method  of  Finding  Flange  Area 

In  the  approximate  method,  the  moment  of  inertia  is  twice 
the  net  area  of  the  flange,  a,  times  the  square  of  half  the  dis- 
tance, h,  between  centers  of  gravity  of  flanges.  This  neglects 
moment  of  inertia  of  web  and  flanges  about  their  own  centers 
of  gravity  as  already  explained.  Moreover,  it  assumes  that 
distance  to  most  strained  fiber  is  equal  to  \h.  Substituting  in 
flexure  formula  already  given: 


(e)    Approximate  Method  of  Determining  Rivet  Spacing 

To  investigate  the  rivet  spacing  by  this  method,  let  a  built- 
up  beam,  Fig.  54*',  be  subjected  to  the  bending  moments  MI 
and  M%  at  distances  /  apart.  Let  V  be  the  average  shear  for 
that  interval.  As  already  shown  the  flange  rivets  have  to  'carry 
the  change  in  stress  between  the  two  sections.  Now  the  stress 
at  left  section  is  M\/h\  at  right,  M2/h\  their  difference  is: 

(M2-M1)/h. 

But  M  2 = MI  +  VI, 

M1+Vl—]tfl     YI 
hence,  5=         — -. 

Shear  per  lin.in.  =  s=S/l  =  V/h.    This  must  be  combined  with 
vertical  shear  as  before. 

(/)    Intermediate  Method  of  Finding  Flange  Area 

An  intermediate  method  of  finding  flange  area  is  to  consider 
that  the  web  carries  its  share  of  the  moment  and  that  the  center 


154 


ELEMENTS  OF  STRUCTURAL  DESIGN 


to  center  of  gravity  of  flanges,  the  depth  of  web,  and  twice  the 
distance  from  neutral  axis  to  most  strained  fiber,  are  all  alike. 
Then, 


or 


S=Mc/I=Mty 

_M__th 
a~~Sh~6' 


S>  = 


where  /  is  the  thickness  of  the  web. 

To  allow  for  holes  in  the  web,  f  is  made  J.  That  is,  in  this 
method,  we  use  approximate  formula  except  that  we  deduct  f 
gross  area  of  web  from  flange  area  required. 


(g)    Example  Showing  Approximate  Method  of  Computation 

Let  us  now  design  in  medium  steel  a  beam  of  30  feet  span 
to  carry  a  dead  load  of  700  Ibs.  and  a  live  of  5000  both  per  lineal 
foot.  Use  approximate  method  and  stresses  as  given  in  Art.  50. 
Rivets,  |  inch  dia.  Estimating  dead  load  of  beam  at  300  Ibs. 
per  lin.ft.: 

Min.              1000 
i+—  —  =1+ =  1.08. 


2  Max. 


2 • 6OOO 


To  obtain  economical  depth,  we  will  assume  a  f"  web  and 
multiply  its  area  by  1.65  to  allow  for  stiff  eners  and  fillers.  For 
flanges,  we  will  use  for  comparison  net  area  required. 

M  =  6000  -30  -30  -i  2/8  =  8, 100,000  in.  Ibs. 


M/Sh 

Depth, 
Web. 

Area  Web. 
Sq.  In. 

Area  X  1.65. 
Sq.  In. 

Effective 
Depth. 

Flange 
Area 
Required. 

Area  X  2. 
Sq.  In. 

Total  Area. 
Sq.  In. 

Sq.  In. 

30" 

11.25 

18.6 

28" 

26.8 

53-6 

72.2 

36 

I3-50 

22.3 

34 

22.0 

44.0 

66.3 

42 

15-75 

26.0 

40 

I8.7 

37-4 

63-4 

48 

18.00 

29.7 

46 

I6.3 

32.6 

62.3 

54 

2O.  25 

33-4 

52 

14.4 

|     28.8 

62.2 

60 

22.50 

37-i 

58 

12.9 

25-8 

62.9 

THE  ENGINEERING  DEPARTMENT  155 

The  theoretic  minimum  occurs  between  48"  and  54"  and 
verifies  proof  in  Art.  52.  We  will  take  the  former.  Its  weight 
per  foot  adding  20%  for  rivet  heads  and  bracing,  will  be: 

62.3-1. 20-3.4  =  254  Ibs. 

Proceeding  with  design: 

Gross  area  required  in  shear  =  6000 -30/2  '7200  =  1 2. 5  sq.in. 
Necessary  thickness  of  web  =  12. 5/48  =  0.26".  Use  f",  the 
minimum  allowable.  Net  area  required  in  each  flange  is  16.3 
sq.in.  Using  a  section  like  Fig.  54^,  and  deducting  one  i" 
dia.  rivet  hole  in  each  angle  and  two  in  each  plate, 

2  Ls,  6"x6"Xi".     Gross  area  =  11.50.    Net  =  10.50  sq.in. 
i  PL  14  Xi".  7.00  6.00 

Total,  18.50  16.50 

Back  to  back  of  flange  angles  will  be  made  48.5".  Distance 
between  centers  of  gravity  is  then: 

48.5  —  2(10.50- 1.68  —  6.00-0. 25)716. 5=46. 5". 

End.            6'  out.  12'  out. 

Vertical  force  on  rivets  per  lin.  in 500              500  500 

Maximum  shear  in  pounds 90,000         57,ooo  30,000 

Horizontal  shear  in  pounds  per  lin.in.  =  V/h . .     i  ,960           i  ,240  650 

Resultant  shear  per  lin.in 2,020           1,340  820 

Spacing,  rivet  value  4710  Ibs 2.34"           3.50"  5-75" 

Values  of  rivet,  |-f -14,400=4710  Ibs.  in  bearing 
2Tc(7/i6)2-7,2oo=864o  Ibs.  shear 

Computation  for  vertical  rivets  is  similar.  Considering 
increments  of  stress  as  proportional  to  areas,  which  is  approx- 
mately  true,  shear  per  lin.in.  between  plate  and  angle  equals: 

area  of  cover  plates  V 
area  entire  flange      ti 
The  vertical  force  is,  of  course,  zero. 

Distance  from  end o  6          12  feet 

V/h 1960        1240        650  Ibs.  per  lin.in. 

6.00 

Area  cover  pls./area  flge.  =  — — =  .364 
16.50 

V 
.3647* 7io          450        230  Ibs.  per  lin.in. 

Value  of  two  rivets  in  single  shear  8640  Ibs. 

8640/shear  per  lin.in.  =  spacing 12.2         19.2        37.5  ins. 


156 


ELEMENTS   OF  STRUCTURAL  DESIGN 


(ti)   Same  Problem,  —  Exact  Method 

Now  let  us  try  the  same  problem  by  the  exact  method, 
assuming  equal  depth.  Computation  for  the  web  will  remain 
unchanged.  We  next  test  the  flanges,  assuming  7/1 6"  metal 
therein : 

I  for  web         =  f*«  1/12- 1-48-48-48  =  2590 

1  for  4  1^6X5  =  4-4.62(24.25  — i.66)2  =  943o 

2  cov.  pis.        =i2-f (24.25+0.22)2    =6310 

Total  in  inches,  18,330 

S  =  Mc/I  =  8,100,000- 24.69/18,330  =  10,900  Ibs.  per  sq.in. 

Spacing  of  horizontal  rivets  in  flanges: 
Statical  moment:   For  2  Ls  2-4.62(24.25  — 1.66)     =209 
i  PI.  ^5-12(24.25+0.22)  =  128 

Total,  2az  =337 

Distance  from  end,  feet o  6  12 

Vertical  shear  per  lin.in 500  500  500 

Shear 90,000  57,ooo  30,000 

2az//  =  .oi84.     Hor.  shear  per  lin.in.  =  .01847=     1,660  1,050  550 

Resultant  per  lin.in 1,730  1,160  740 

Spacing  =  47 1  o/resultant 2.72  4.05  6.40 

Spacing  of  vertical  rivets : 

Here  there  will  be  no  vertical  force. 

Distance  from  end,  feet o  6  12 

Shear  as  before 90,000         57,ooo         30,000 

Zaz/I  = =.00698 

18330 

Hor.  shear  per  lin.in 630  400  210 

Value  of  two  rivets  in  single  shear  8640 

864o/shear  per  lin.in.  =  spacing 13.7  21.6  41.0 

However,  spacing  must  not  exceed  6"  or  4^"  if  staggered 
(Art.  50  ei). 

In  above  problems  it  has  been  assumed  in  all  cases  that 
top  flange  is  properly  supported.  (Art.  50  dn.) 

Tables  in  handbooks  are  often  a  great  help  in  the  computa- 

*  Deductg  |in  for  holes. 


THE  ENGINEERING  DEPARTMENT  157 

tion  of  beams.     Capacity  under  uniform  loading  for  all  the  shapes 
and  some  girders  may  be  found  in  Cambria  or  Carnegie. 

Many  other  examples  will  be  found  in  Vol.  II.  Especially 
important  are  those  given  in  the  Chapters  on  Plate  Girders  and 
Office  Buildings. 


Art.  55.    Design  of  Tension  Members 

These  may  be  of  round  rods,  square  rods,  rectangular  bars, 
angles,  and  built-up  shapes.  There  are  three  ways  in  which  the 
stresses  due  to  its  own  weight  may  be  combined  with  tension. 

(1)  Add  maximum  flexural  stress  to  the  tensile  unit  stress. 

(2)  Take  account  of  the  fact  that  the  weight  and  pull  cause 
a  deflection  at  the  center,  at  which  point  the  moments  are  of 
opposite  kind.     (Fig.  550.) 


FIG.  550.  —  Tie  Acted  upon  by  FIG.  556.  —  Weight  in  an 

its  Own  Weight.  Inclined  Member. 

(j)  Consider  the  varying  eccentricity  of  the  pull. 

Many  engineers  ignore  these  stresses  largely  or  wholly. 
(j)  is  good  enough  for  comparatively  short  and  deep  sections. 
(j)  is  too  complicated  to  be  used  in  practice  and  is  a  needless 
refinement. 

Taking  up  the  second  method,  let  w  be  the  weight  of  the 
bar  per  lineal  inch,  I  its  moment  of  inertia  in  inches,  E  its  modu- 
lus of  elasticity  in  pounds  per  square  inch,  a  its  area  in  square 
inches,  and  /  its  length  in  inches.  The  maximum  moment 
occurs  at  center  of  span  and  is: 


Deflection  due  to  a  bending  moment 

(«=wP/8) 
is  sarf*/384fi/  =  (m 


158  ELEMENTS  OF  STRUCTURAL  DESIGN 

Assuming  now  that  the  deflection,  d,  bears  a  similar  ratio  to 
its  moment,  M: 

M  =  (wl2/S)-$Pl2M/4&EI    or    M  = 
S-=  Me  1  1  =  wl2c/S  (I  +  sPl2/4SE)  . 
For  a  rectangle  this  becomes, 
5  = 


where  b  =  breadth  and  h  =  depth,  both  in  inches. 
To  obtain  maximum  stress,  this  must  be  added  to  direct  stress. 
In  the  case  of  an  inclined  member,  Fig.  55^,  weighing  w  per 
lineal  unit,  let  any  elementary  weight,  m,  be  resolved  into  com- 
ponents m  sin  6  causing  direct  stresses  which  are  small  and  may 
be  ignored,  and  m  cos  0  causing  bending  stresses.  The  maximum 
bending  moment  will  occur  at  the  middle  and  be  equal  to 

wl2  cos  0 


where  /  is  inclined  length  of  member. 

Square  or  round  rods  are  easily  fabricated  and  erected. 
They  are  usually  adjustable  and  hence  may  work  loose.  Also 
their  lack  of  stiffness  makes  them  likely  to  rattle.  Square  rods 
can  be  turned  with  an  ordinary  wrench  whereas  a  pipe  wrench 
is  required  for  a  round.  However,  the  latter  fact  may  be  an 
advantage  if  they  are  within  ready  reach. 

Let  it  be  required  to  design  a  steel  rod  for  a  tension  of  46,000 
Ibs.  Allowable  stress,  12,000  Ibs.  per  sq.in.  £  =  30,000,000 
Ibs.  per  sq.in. 

Area  required  =  46  ,000/12,  000  =  3.  83  sq.in.  Use  2"  square 
or  2\"  round.  Supposing  now  the  square  rod  to  be  20  feet 
long,  let  us  investigate  stress  due  to  own  weight  which  is  1.13 
Ibs.  per  lin.in. 

3-I.I3-240-240-2 


4&/J3  +  $PP/E       4  •  2  •  8  +  (5  •  46,000  •  240  •  240)  730,000,000' 

=  774  Ibs.  per  sq.in.   and  the  rod  should  be  made  ITS" 
square  instead. 


THE  ENGINEERING  DEPARTMENT  159 

For  locations  where  members  will  always  be  in  tension, 
rectangular  bars  are  now  the  accepted  design.  Where  idle  or 
likely  to  take  some  compression,  the  best  practice  favors  using 
compression  shapes.  Sometimes  bars  themselves  are  "  counter- 
braced  "  that  is,  fastened  together  to  resist  some  compression. 
These  bars  have  their  ends  enlarged  to  provide  connection  for 
pins  and  are  then  known  as  eyebars,  Art!  43.  Thickness  should 
not  be  more  than  \  its  depth  in  order  to  give  a  well  packed  joint  ; 
it  should  not  be  under  1/7  to  prevent  weakness  on  compression 
side  as  a  beam  under  its  own  weight. 

Let  us  design  an  eyebar  for  a  pull  of  88,000  Ibs.  and  an  allow- 
able stress  of  15,000  Ibs.  per  sq.in.  Bar  is  30  feet  long,  and 
inclined  at  an  angle  of  30  deg.  with  horizontal.  Use  first  method. 

88,000/15,000  =  5.87  sq.in.  area  required. 
Try  a  6"XiA",  area  =  6.37  sq.in.     Wt.  per  lin.in.  =  i.8i  Ibs. 
Direct  stress         =88,000/6.37  =  13,800  Ibs.  per  sq.in. 
Bending  moment  =  wl2  cos  0/8  =  1.81-360  -360  -.866/8. 
=  25,400  in.  Ibs. 

Ibs.  per  sq.in. 


As  this  stress  will  remain  constant  for  the  same  depth,  we 
can  increase  width  and  allow  11,000  Ibs.  per  square  inch  for 
direct  stress. 

88,000/11,000  =  8.00  sq.in.,  use  6"Xif". 

Probably  a  7"  bar  would  be  more  economical. 

Angles,  singly  or  hi  pairs,  are  used  a  great  deal,  either  for 
wind  bracing  or  small  trusses.  They  do  not  bend  or  rattle 
like  rods  and  they  will  stand  some  compression.  Let  us  design. 
a  pair  of  angles  for  the  same  data  as  the  square  rod. 

46,000/12,000  =  3.83  sq.in.     Use  2  Ls  5"X3"Xi%". 

Gross  area,  4.80  sq.in. 

Deducting  2  holes,  each  J"x&"  for  J"  rivets: 

Net  area  =4.26  sq.  in. 

Direct  stress  =46,000/4.  26  =  10,800  Ibs.  per  sq.in. 


160'  ELEMENTS  OF  STRUCTURAL  DESIGN 

» 

Stress  due  to  its  own  weight,  assuming  longer  legs  vertical; 
1.37-240-240- 


0 
sq.n.  48-30,000,000    / 

Total  stress  is  10,800+760  =  11,560  Ibs.  per  sq.in. 

There  are  two  common  types  of  the  built-up  tension  member, 
the  I,  Fig.  567  or  g,  and  two  channels,  either  rolled,  Fig.  56;  or 
k,  or  built  up  as  in  Fig.  $61  or  m.  The  former  consists  of  four 
angles  united  either  by  a  single  continuous  plate,  by  batten 
plates,  or  by  lacing.  Cover  plates  may  be  added  top  and  bottom. 
The  I  is  a  favorite  section  for  bracing  capable  of  carrying  com- 
pression, and  for  the  web  tension  members  of  riveted  trusses. 
The  solid  I  should  not  be  used  where  its  web  will  be  horizontal 
because  so  placed  it  retains  water. 

For  heavier  stresses,  use  one  of  the  two  channel  sections. 
These  are  united  top  and  bottom  by  lacing  or  batten  plates. 
Flanges  may  be  turned  either  way  as  determined  by  conditions 
at  joints  or  clearance  for  riveting.  Plates  shown  dotted  may  be 
added  to  increase  strength. 

As  an  example,  let  it  be  required  to  design  in  soft  steel 
according  to  specifications,  Art.  50,  a  built  I  section  for  a  max- 
imum tension  of  142,000  Ibs.  and  a  minimum  of  20,000.  Member 
will  be  25  feet  long  and  vertical. 

Allowable  stress  is  9000(1  +  20,000/2- 142,000)  =9650  Ibs. 
per  sq.in. 

Net  area  required  =  142,000/9650  =  14.7  sq.in. 

Use  i  PL  14"  X  A".      Gross  area  6.12  deduct  for  2  I"  rivets. 
4Ls5/'X3//xr.  11.44  4 

Net  area,  15.19  O.K. 

Where  a  riveted  section  is  horizontal  or  inclined,  stress 
due  to  own  weight  may  be  very  nicely  taken  care  of  by  giving 
connection  such  an  eccentricity  that  its  moment  balances  that 
of  the  weight. 


THE  ENGINEERING  DEPARTMENT  161 


Art.  56.    Design  of  Compression  Members 

The  desirable  features  in  a  column  are: 

(1)  Favorable  disposition  of  the  metal,  that  is,  that  dis- 
position, which,  for  a  given  area,  makes  radius  of  gyration  a 
maximum. 

(2)  Economy  of  shopwork.     Columns  are  usually  expensive 
to  fabricate. 

(j)  Easy  end  and  intermediate  connections. 

(4)  Connections  which  give  centrally  applied  loads.     Even 
if  eccentricities  balance,  live  load  on  one  side  only  may  change 
this. 

(5)  In  many  places,  it  is  desirable  that  the  column  should 
be  as  compact  as  possible. 

(6)  A  section  enclosed  on  all  sides  is  objectionable,  since 
it  is  inaccessible  either  for  inspection  or  repair. 

(7)  Out  of  doors,  all  steel  work  should  be  so  designed  that 
it  will  not  retain  water. 

Let  us  now  consider  the  different  types  of  columns  in  the 
light  of  the  above.  Taking  up  first,  columns  of  a  single  shape. 

(a)  Angle.  (b)  Zee  bar. 

These  have  small  radii  of  gyration  and  are  limited  to  short 
columns  and  low  stresses.  Except  for  (j),  they  are  desirable 
in  every  way. 

(c)  Channel. 

This  has  a  small  radius  of  gyration  one  way,  but  a  large 
moment  of  inertia  the  other.  It  is  hence  suited  for  small 
compressive  stresses  when  combined  with  bending.  Employed 
for  struts  at  eaves  of  buildings  and  ends  of  bridges.  Desirable 
in  every  way  except  (i). 

(d)  I-beam. 

This  is  much  like  the  channel  but  it  has  a  larger  radius  of 
gyration  and  better  withstands  bending.  We  find  it  used  for 
larger  compressions  and  bending  moments  as  in  a  column 
supporting  the  roof  of  a  mill  building.  It  is  not  as  convenient 
for  shopwork  and  connections  on  two  sides  are  quite  eccentric. 

(e)  H  section. 

The  rapidity  with  which  this  column  has  sprung  into  favor 


162  ELEMENTS  OF  STRUCTURAL  DESIGN 

for  moderate  loads  is  explained  by  its  advantages.  The  metal 
is  well  disposed,  there  is  no  shopwork  except  at  connections 
and  these  are  quite  easy  and  fairly  central,  they  are  compact, 
are  not  enclosed  and  will  not  hold  water  unless  placed  horizon- 
tally. We  know  of  but  one  objection  to  them,  they  cost  about 
$0.20  per  hundred  weight  more  for  the  raw  material. 
Taking  up  now  the  built-up  sections, 

(f)  Two  angles  riveted,  Fig.  560. 

The  piece  between  the  angles  shows  a  washer  filler,  Fig. 
37&,  which  may  be  inserted  at  intervals  or  omitted  altogether. 
This  section  is  more  economical  if  placed  with  the  short  legs 
outstanding.  Its  characteristics  are  much  like  those  of  a  single 
angle  column  but  the  radius  of  gyration  is  a  little  larger  and 
shop  work  is  more  expensive.  Suitable  only  for  short  members 
and  light  loads.  Employed  for  wind  bracing  and  roof  trusses. 

(g)  Two  angles  and  a  plate,  Fig.  566. 


JL 


FIG.  560  FIG.  566.  FIG.  560. 

Two  Angles.       Two  Angles  and  a  Plate.  Four  Angles  Riveted. 

Column  Sections. 

Much  like  (/)  except  that  it  is  des'gned  to  carry  bending 
moment  in  addition  to  compression.  Used  for  the  top  chord 
of  roof  and  riveted  trusses.  This  section  might  also  be  employed 
for  tensile  stresses. 

(ti)  Four  angles,  riveted,  Fig.  56^. 

These  are  fastened  together  as  shown  with  batten  plates 
at  intervals.  It  is  economical  .of  space,  but  metal  is  very 
poorly  placed,  shopwork  is  fairly  high,  connections  are  difficult 
and  eccentric,  and  column  is  full  of  pockets.  An  undesirable 
section. 

(i)  Four  angles  latticed  or  battened.     Figs.   56 d  and  e. 

The  material  of  the  section  is  well  placed,  but  the  proportion 
of  details  which  do  not  carry  weight  is  very  high,  shopwork 
is  expensive,  connections  are  difficult  and  costly.  Used 
principally  in  long  unbraced  columns  where  it  is  important 
to  keep  weight  low  as  in  derricks. 


THE  ENGINEERING  DEPARTMENT 


163 


0')  Built  I-beam,  latticed,  Fig.  567. 

The  shorter  leg  of  the  angle  should  be  parallel  to  lacing 
for  economy.  Material  is  not  well  disposed  and  cost  of  details 
is  high.  It  is  used  in  locations  where  the  stress  is  small  and 
depth  is  demanded  for  sake  of  connections  or  to  resist  stresses 
due  to  own  weight  as  in  the  bracing  for  a  bridge. 

(k)  Built  I-beam,  solid,  Fig.  $6g. 

Here  there  is  less  waste  material  than  in  (j).  Plates  shown 
dotted  increase  allowable  unit  stress  as  well  as  area.  The 
radius  of  gyration,  however,  still  continues  small,  and  it  is  not  a 
very  economical  section.  Shopwork  is  moderate  for  either. 
Connections  are  easy  but  eccentric  on  two  sides.  Used  as  col- 
umns in  buildings  and  in  web  members  of  riveted  truss  bridges. 


FIG.  5&/.  FIG.  560. 

Four  Angles  Latticed  or 
Battened. 


FIG.  s6/.      FIG.  s6g. 

Built  Fs 
Latticed         Solid. 

Column  Sections. 


FIG.  56^.    FIG.  56*. 
Three  I  Two  Channels 
Beams,      and  One  I. 


(/)  Three  I-beams,  Fig.  56/2. 

This  section  seems  quite  desirable  but,  on  account  of  the 
slightly  greater  advantages  of  (m),  is  not  common. 

(m)  Two  channels  and  one  I-beam,  Fig.  562'. 

As  in  (/),  section  is  Very  well  placed,  it  is  economical  of 
shopwork,  and  easy  to  connect  with.  While  either  is  likely 
to  have  eccentric  connections  on  two  sides,  they  are  well  able 
to  bear  this.  It  is  not  a  closed  section,  and  it  does  not  hold 
water  if  placed  vertically.  It  does,  however,  occupy  con- 
siderable room,  (/)  slightly  more  than  (m),  and  former  is  also 
a  little  harder  to  handle.  They  are  ideal  where  a  moment  in 
both  directions  is  to  be  carried,  as  in  columns  for  cranes  and 
elevated  railroads.  Obviously,  either  (7)  or  (m)  may  be  built  up. 

(ri)  Two  channels,  latticed,  Figs.  56;  and  k. 

Metal  is  well  placed  but  shopwork  and  weight  of  details 
are  moderately  high.  Connections  are  fairly  easy  and  this 
type  is  frequently  used  as,  for  example,  in  parts  of  bridges 


164 


ELEMENTS  OF  STRUCTURAL   DESIGN 


and  columns  for  buildings.  Extra  plates  may  be  added  either 
outside  or  inside  as  shown  by  dotted  lines. 

(0)  Two  built  channels,  latticed,  Figs.  $61  and  m  . 

Very  much  like  (ri)  except  that  shopwork  is  higher  and  that 
it  is  used  where  the  rolled  shapes  will  not  provide  the  necessary 
area. 


n 


i -i 


n 


FIG.  56;.        FIG. 
Two  Channels, 
Latticed. 


FIG.  56/.         FIG.  s6m. 

Two  Built  Channels, 

Latticed. 

Column  Sections. 


FIG.  56^.          FIG.  560. 
Two  Channels  and 
Cover  Plate. 


(p)  Two  channels  and  a  cover  plate,  Fig.  56^. 

Channels  are  turned  as  shown  and  may  be  rolled  or  built- 
up.  Plates  may  be  added  as  in  (0)  or,  if  nothing  interferes, 
angles  may  be  added  on  the  inside,  Fig.  560.  Material  is  well 
placed,  shopwork  moderate,  open  for  inspection,  and  especially 
suited  for  easy  and  efficient  connections  in  the  top  chords  of 
bridges  where  it  is  the  accepted  design. 

(q)  Built  I  and  two  built  channels,  Fig. 


FIG.  $6p 
Built  I  and  Two  Built  Channels. 


L 

FIG.  56?. 
"Box." 

FIG.  s6r. 
Zee  Bar. 


Column  Sections. 


To  still  further  increase  capacity,  one  or  more  built  I's 
may  be  inserted  between  channels  in  (0),  and  in  a  similar  way 
extra  plates  could  be  added.  As  in  (p),  one  might  rivet  on  a 
cover  plate  in  place  of  lacing. 

(r)  Box  column,  two  channels  and  two  cover  plates,  Fig. 
56*?.  Channels  are  either  rolled  or  built  up.  Material  is  very 
well  placed,  shopwork  moderate,  connections  easy,  but  they  are 
quite  eccentric,  and  it  is  a  closed  column.  Used  in  building 


THE  ENGINEERING  DEPARTMENT  165 

work,  where  it  should  always  be   incased    in  fireproofing    to 
ensure  against  rust. 

(s)  Zee-bar  column,  Fig.  $6r. 

Here,  the  theoretic  disposition  of  the  metal  is  very  good, 
but  under  test  the  outside  corners  fail  first  because  they  are 
insufficiently  stayed.  Connections  are  central  and  easily 
arranged.  Is  accessible  for  inspection  except  when  plates 
shown  dotted  are  added  to  secure  increased  strength. 

Among  the  remaining  types  of  columns,  we  may  mention 
the  Phcenix,  now  obsolete,  and  the  Larimer, 
Fig.   22g,  both    of  which    are   explained   in 
Art.  22. 

As  an  example  of  how  large  columns  are 
built  up,  we  give  Fig.  565.*     This  shows  a 

section  of  the  bottom  chord  of  the  Quebec     ,, 

,.,        ,«•*  .,  *     !•  v  j      FIG.  565.—  Section  of 

cantilever  bridge,  the  failure  of  which  caused        ^  Bottom  Chord 

the  wreck  of  the  structure.     (Art.  69.)     The        of  the  Quebec  Can- 
outer  ribs  were  made  of  2  L's,  8"x6"xif",        tilever  Bridge. 
i   PL   54"  Xf,    2    Pis.     54"  Xif",    and    i 
PI.  37f"Xit".     The  inner  ribs   were   2  L's,   S"Xti"X$",   2 
Pis.   54"Xli",  2  Pis.  46"  Xtt".    Lacing  was  double,  45  deg., 
of  i  L  4"X3"Xi"  and  cross  struts,  i  L  3J"X3"X|". 

In   design,   the   author  prefers   the   straight  line   formula, 


where  P  is  total  load  and  A  gross  area;  //p,  the  greatest 
slenderness  ratio,  that  is,  the  greatest  value  of  the  fraction, 
unsupported  length  divided  by  corresponding  radius  of  gyration. 
Ci  is  the  unit  strength  for  a  short  strut  and  Cz  is  a  constant 
for  a  given  material  which  will  bring  the  straight  line  tangent 
to  Euler's  curve  for  long  columns.  We  have  made  €2  a  little 
large,  about  .006,  in  order  to  discourage  the  use  of  long  slender 
columns. 

The  stress  due  to  own  weight  may  be  taken  care  of  as  in 
tension  members.  However,  the  moment  due  to  the  load  P 
(see  preceding  article),  is  plus  instead  of  minus  and  hence  the 
formula  becomes: 

S  =  w*V8(I  -  5P/2/48E)  . 

*  Engineering  News,  Vol.  LVIII,  p.  320. 


166  ELEMENTS  OF  STRUCTURAL  DESIGN 

It  is  customary  in  main  members  to  give  the  connection  just 
enough  eccentricity  to  balance  the  stress  due  to  own  weight  as 
already  mentioned  for  ties. 

Let  us  take  up  now  the  fastening  together  of  the  parts  of  a 
built-up  column.  In  the  first  place,  the  distance  between  the 
points  at  which  the  parts  are  riveted  should  be  such  that  the 
slenderness  ratio  for  none  of  those  parts  exceeds  that  for  the 
column  as  a  whole. 

To  obtain  strength  required  for  this  fastening  whether  of 
lacing  or  rivets,  let  us  consider  the  above  formula, 


The  reason  why  long  columns  fail  at  lower  unit  stresses 
than  short  ones  of  the  same  cross-section  is  that  irregularities 
of  manufacture  cause  an  eccentricity,  the  effect  of  which  is 
similar  to  a  uniform  load  applied  at  right  angles  to  the  column. 
The  transverse  load  causes  a  bending  with  compression  on  one 
side  and  tension  on  the  other,  and  post  fails  when  sum  of  com- 
pressions due  to  flexure,  Si,  and  axial  load,  S2,  reaches  Ci. 


or 

Si=CiC2//p. 
But 


assuming  that  load  which  causes  bending  moment  is  uniform. 
Where  W  =  uniform  load  applied  transversely,  and 

c  =  distance  from  neutral  axis  to  most  strained  fiber. 
Equating  these  two  values  of  Si,  and  substituting  4p/3,  a 
rough  value,  for  c, 


Taking  for  C2,  the  value  .006, 


or  about  one-thirtieth  load  on  a  short  strut  of  same  section. 
Some  of  the  assumptions  made  in  the  proof  might  be  questioned 
on  theoretic  grounds  but  the  fact  remains  that  the  rule  here 
deduced  agrees  very  well  with  present  practice. 


THE  ENGINEERING  DEPARTMENT 


167 


In  addition  to  specifications  in  Art.  50,  ^3,  and  04,  the 
follow'ng  should  be  noted.  Lacing  may  be  single,  inclined  at 
an  angle  of  about  60°  with  axis,  and,  if  there  are  two  sets, 
staggered  as  shown  in  Fig.  56/5  or  double,  at  an  angle  of  45°, 
Fig.  561*.  In  either  case,  it  should  be  figured  as  a  truss.  How- 
ever, as  it  is  more  economical  to  make  all  piprps  alike,  only 


FIG.  562.  FIG.  562*.  FIG.  $6v.  FIG.  5620. 

Arrangement  of  Lattice  Bars.  Showing  Use  of  Batten  Plates. 

maximum  stress  in  end  member  need  be  computed.  Lattice 
bars  are  often  placed  as  in  Fig.  562,  but  it  does  not  seem  like  an 
effective  arrangement;  we  must  admit  that  it  is  employed  in 
good  work.  As  already  mentioned,  occasional  batten  plates 
are  sometimes  inserted  in  place  of  lacing,  Fig.  5670;  nevertheless, 
as  may  be  inferred  from  above  analysis,  it  is  inefficient  and 
unsuitable  for  important  locations. 

The  lattice  bars  vary  in  size  from   4"xi"  to   2^"xf" 
and  even  larger  for  built-up  columns.     Angles  may  be  used  to 


FIG.  56*. 
Forms  of  Lattice  Bars. 


FIG.  56^.  FIG.  562. 

Arrangements  of  Batten  Plates  and  Lattice  Bars. 


advantage  in  very  large  compression  members.  Fig.  560: 
shows  different  ways  of  making  the  bars.  The  center  of  the 
curve  is  seldom  at  the  rivet  but  nearer  the  outer  end. 

The  latticing  should  start  either  from  the  batten  plates, 
Fig.  56%  or  from  a  rivet  as  close  to  it  as  clearance  will  allow, 
Fig.  562.  Lattice  bars  may  be  used  where  the  surfaces  with 
which  they  connect  are  not  in  exactly  the  same  plane.  For 
example,  the  lattice  bar  in  Fig.  56^  might  run  from  on  top 
of  the  batten  plate  to  top  of  channel. 


168 


i 

ELEMENTS  OF  STRUCTURAL  DESIGN 


Let  it  be  required  to  design  a  medium  steel  single  shape 
column  8  ft.  long  according  to  specifications  in  Art.  50.  Load 
is  50,000  Ibs.  dead. 

Allowable  stress,  15,000  (i  — .006  //p). 

Maximum  //p  =  ioo,  minimum  p  =  o.96". 

All  zee  bars  and  channels  have  lower  radii  of  gyration,  but  we 
can  use  any  equal  legged  angle  above  a  4"X4"  and  any  I  beam 
above  10"  in  depth. 


Section. 

Weight 
per  Foot. 

P 

Allow. 
Stress. 

Area. 

Total 
Stress. 

Remarks. 

*iL5X5X  7/8 

27.2 

0.96 

6000 

7-99 

48,000  # 

Too  low 

*iL  5X5X15/16 

28.9 

0.96 

6000 

8.50 

5  1,  OCX)* 

O.K. 

•  iL  6X6X11/16 

26.5 

I.I7 

7620 

7.78 

59,300  # 

Too  high 

iL6X6X  5/8 

24.2 

1.18 

7680 

7.11 

54,600  # 

O.K. 

IL6X6X  9/16 

2I.Q 

1.18 

7680 

6-43 

49.300  # 

Too  low 

iL8X8X  1/2 

26.4 

1-58 

9570 

7-75 

74,000  # 

il  10 

2<    O 

web  too  t 

hin 

ll    12 

•jtr    o 

o  oo 

6270 

IO    2O 

64,700  $ 

Everything  in  pounds  and  inches. 

Number  4  should  be  used.  We  need  not  have  tried  numbers 
6  and  8,  after  we  had  found  their  weight  unless  a  surplus  of 
strength  were  desirable.  In  this  case  we  should  use  6,  as  it 
has  a  larger  capacity  and  less  material  than  8. 

Next  we  will  compute  the  size  required  for  a  medium  steel 
column  of  two  channels  latticed  with  flanges  turned  out.  Speci- 
fications as  in  Art.  50.  Post  is  vertical  and  25  feet  long  .Loads 
range  between  1 1 2,000  compression  and  25,000  tension.  Estimat- 
ing allowable  stress  at  6000,  about  19  square  inches  will  be 
needed.  Let  us  try  2  channels  i5"at  33  Ibs. 

Allowable  stress 

=  10,000(1  —  25,000/2  •  1 12,000)  (i  —  .006  •  300/5.62) 

=  6040  Ibs.  per  sq.in. 
Area  required  =112,000/6040  =  18.5  sq.in. 

*  Special  sections  and  undesirable  on  that  account.  Also  so  thick  it  would 
have  to  be  drilled  (Art.  44). 


THE  ENGINEERING  DEPARTMENT 


19.8  are  furnished,  so  this  is  O.K.     There  is  plenty  of  metal  for 
tension. 

To  design  the  latticing,  let  us  take  it  as  single  and  inclined 
at  60°  with  the  axis.  Gage  to  gage  will  be  about  13.25''  and 
the  unsupported  length  of  the  bars  will  be  13.25  sec  30°  =  15.3". 
Assuming  f "  thickness,  the  allowable  stress  is, 

10,000(1  —  25,000/2  •  112,000)  (i  —  .006-  i5.3/.io7)  =  1 260  Ibs.  per  sq.in. 
Transverse  load  is 

(10,000/30)    (1  —  25,000/2-112,000)    (19.8)  =5850  Ibs. 
Stress  at  either  end  is,  5850  sec.  3o°/4  =  1690  Ibs. 

1690/1260  =  1.34.  Use  3X15",  area  1.31  sq.in.  Amply  safe 
with  depth  larger  than  assumed. 

Now  let  us  determine  sizes  for  a  two-channel  and  a  plate 
section  of  medium  steel,  Fig.  56^.  Length,  20  feet;  maximum 
load  280,000  Ibs.  C;  minimum  load,  80,000  Ibs.  C. 
Specifications  as  hi  Art.  50. 

Assume  allowable  stress  to  be  9000  Ibs.  per 
sq.in.  FlG> 

Then  area  required  will  be  280,000/9000  equals 
31  sq.in.     Let   us   try  section  shown  in  Fig.  5600,  horizontal 
distance  in  clear  between  plates,  10". 


Distance  to 

Static 

/ 

/ 

Size. 

Area. 

Center  of 

Moment. 

Moment. 

Moment. 

Gravity. 

XX 

XX 

YY 

a.  i  PI.    i8X| 

6-75 

8-31 

+  56.1 

466 

182 

b.  2  Pis.  i6X| 

12.00 

00 

00 

256 

323 

c.  2Ls.  3^X31X1 

4.96 

.    7-n 

+35.3 

257 

212 

d.  2  Ls.  3^X35X1 

7.96 

7.02 

—  56.0 

402 

335 

For  entire  section.  .  .  . 

31.67 

I  .12 

+35-4 

1381 

1052 

Everything  in  inches. 

Ixx  about  e.g.  =  1381 -31.67 -i. 12 -i. 12  =  1341. 
=  (1052/31.67)*  =  5.75  in. 


170 


ELEMENTS  OF  STRUCTURAL  DESIGN 


Allowable  unit  stresses 

=  10,000(1  +80,000/2  •  280,000)  (i  —  .006  •  240/5.75) . 

=  8570  Ibs.  per  sq.in. 
Total  allowable  stress 

=  31.67-8570  =  272,000  Ibs. 

This  is  too  low.     We  will  use  bottom  angles  tJ"  thick,  making 
total  quantities: 

•Area,  32.39;   distance  to  center  of  gravity,  0.96";    statical 
moment  about  XX,  30.9;   /  about  center  of  gravity,  horizontal 


FIG.  $6ab. — Typical   Column.     Upper    Chord   of    Pin-connected    Truss    Bridge, 
American  Bridge  Co.,  Ambridge,  Pa. 

axis,  1383;    7Fy,  1096;     p,  5.80";    allowable  unit  stress  8590; 
total  allowable  stress,  278,000  Ibs.;  will  do. 

Allowing  40%  for  extras,  weight  per  foot  will  be  154  Ibs. 
Deflection  =  $WP/$%4EI 

=  5  •  3080-240-  240-  240/384  30,000,000  •  1383  =  .013" 
M  due  to  own  weight  =  3080-  240/8  =  92400  in.  Ibs. 


THE  ENGINEERING  DEPARTMENT 


171 


Amount  which  the  center  of  gravity  of  the  column  should 
be  placed  above   the  intersection 
point  is, 

.013+92,400/280,000  = 

.342  or  about  f ". 

It  will  be  noticed  that  any 
additional  plates  that  may  be 
necessary  will  be  located  on  the 
side  at  a  distance  from  the  center 
about  equal  to  the  radius  of  gyra- 
tion. Therefore  allowable  unit 
stress  will  be  changed  little  when 
reinforcement  is  tacked  on.  In 
practice,  for  a  case  like  this,  allow- 
able stress  need  not  be  recom- 
puted. 

Latticing  must  be  figured  for  a 
transverse  load  of, 

10,000(1  +80,000/2  •  280,000) 

32.39/2-30  =  6200  Ibs., 

the  other  half  being  carried  by  the 
top  plate.  Maximum  shear  is  3100 
Ibs.  at  each  end.  Latticing  is 
usually  made  double,  45°,  and 
riveted  at  the  center.  Stress  in 
end  bar  is  then  3100  sec.  45°/2  = 
2190  Ibs.  Unsupported  length  is 
about  7!  sec.  45°  =  n//. 

Let  us  try  a  3X&",  9  =  0.09". 
Allowable  total  stress  equals  2860 
Ibs.  O.K.  A  2JX|"  would  be  as 
cheap  and  much  more  efficient. 

While  lacing  bars  are  usually 

weakest  in  compression,  rivets  and  tensile  stresses  should  also 
be  watched. 


FIG.  560^:. — Typical  Column.  Ver- 
tical Post  in  Drawbridge,  Ameri- 
can Bridge  Co.,  Ambridge,  Pa. 


172  ELEMENTS  OF  STRUCTUKAL  DESIGN 


Art.  57.    Strain  Sheet 

"  Stress  Sheet  "  would  be  more  appropriate  but  we  follow 
custom. 

The  strain  sheet  gives  a  line  drawing  of  proposed  structure 
with  its  principal  dimensions.  There  should  also  be  a  state- 
ment as  to  loads  assumed,  total  stresses  resulting  therefrom, 
unit  stresses  allowed,  and  sections  designed  for  the  different 
pieces.  Second  and  last  are  usually  placed  directly  on  the 
members  to  which  they  belong.  Title  should  give  name  and 
location  of  designer  and  purchaser.  Date,  scale,  and  name  of 
maker  ought-  also  to  appear  on  the  drawing.  For  lettering, 
see  Art.  62,  also  sample  strain  sheet,  Fig.  57. 

Sometimes  important  or  peculiar  connections  are  drawn  out. 
Often  all  details  are  worked  up,  and  leading  dimensions  and 
material  given.  It  partakes  then  of  the  nature  of  a  detailed 
drawing  and  is  called  a  "  general  plan." 


Art.  58.    Detailing 

Detailing  may  be  divided  into  two  parts: 

(a)  The  design  of  the  small  parts  of  the  structure — rivet 
spacing,  connections,  shoes,  and  so  on,  which  will  be  taken  up 
in  Arts.  59,  60,  and  61,  and  also  in  other  volumes. 

(b)  Structural  steel  consists  of  rolled  shapes,   cut,   forged 
or  bent,  punched  or  drilled,  and  machined.     Specifying  and 
locating  these  form  the  second  part.     See  also  Art.  40. 

There  are  two  general  methods  of  accomplishing  (b).  Take, 
for  example,  a  roof  truss.  In  the  first  method,  we  show  by 
sketch  number  of  rivets  and  method  of  arranging  connections, 
give  center  to  center  distances,  state  material  required,  also 
maximum  and  minimum  spacing  and  edge  distances  and  leave 
templet  shop  to  arrange  details  on  full  size  layout  on  shop  floor. 
This  method  is  cheap,  especially  in  the  drawing  room,  but 
it  renders  control  by  the  engineer  more  difficult.  Also  in  case 
of  repairs  or  alterations,  expensive  measurements  on  site  may 
be  necessary. 


THE  ENGINEERING  DEPARTMENT  173 

S    d 


174 


ELEMENTS  OF  STRUCTURAL  DESIGN 


The  second  method  gives  all  dimensions  required  to  work 
out  each  piece  separately.  Fig.  580  shows  three  different  ways 
in  which  this  may  be  done  for  skew  measurements,  (i)  is 
more  expensive  and  liable  to  error  and  is  used  very  seldom  and 
only  to  prepare  for  rack  punch.  (2)  and  (j)  are  both  good; 


(i)  (2)  (3) 

I"  rivets  ft",  open  holes. 

FIG.  580. — Methods  of  Detailing  Connection  Plates. 


latter  is  a  little  easier  in  drawing  room  and  a  little  more  difficult 
in  shop. 

There  is  still  another  subdivision.  Structures  may  be  detailed 
"  in  place,"  that  is,  with  the  pieces  in  the  relative  position 
which  they  will  occupy  in  the  field.     This  is  easier  to  under- 
stand, but  the  manual  drawing  is  more  diffi- 
cult   and    it    takes    additional   space.      Or 
"  knocked  down  "  with  pieces  taken  apart 
and  given  in  their  most  convenient  position. 
Fig.  586  shows  difference.     It  is  not  common 
to  take  apart  a  shipping  piece. 

Consider  now  the  simple  cases  given 
above.  Fig.  580  shows  details  of  a  plate; 
c,  an  angle;  dt  an  I-beam;  and  e,  a  plate 
girder.  To  enable  shops  to  fabricate  these 
or  other  structures; 

(i)  Bill  material.  Standard  fittings  need  only  be  named. 
For  example,  rivets  are  specified  by  diameter,  given  in  note 
as  shown.  Other  pieces  of  metal  must  be  billed  as  mentioned 
in  Chapter  II.  This  material  is  lettered  on  the  drawing  in 
such  a  place  that  there  will  be  no  doubt  as  to  which  piece  is 


LOR 


L9R 


Knocked  Down 

FIG.   586.— Methods 
for  Laterals. 


THE  ENGINEERING  DEPARTMENT 


175 


intended.     Often  a  table  is  made  at  the  side  giving  the  informa- 
tion, but  unless  an  assembly  or  identifying  mark  is  used,  or 


*  r-lfc-   ...                                                           13  '-<S-c/c«nd  holes                                               _o-lliT. 

5-ii"                         3*                  fl'-IO"                    r3!.                     £'-S±" 

£ 

£"  3'                                 9  -  E  '                                V 

9-O"                            3"  3 

•k" 

|                                                ^-  Oaqe    3*1  — 

! 

» 

1  L  5"x  3i"x|"x.  13'-9 

4   LATERALS    L6 

jfZR 

FIG.  s8c.— Detail  of  an  Angle.— Open  Holes,  W. 

except  for  very  simple  structures,  the  writer  does  not  approve. 
It  is  best  to  place  notation  as  near  piece  as  is  feasible,  with 
arrdws  if  necessary. 


0 

L                                                      7-fe"cb«o 

f 

T-5'o.boo. 

* 

I 

=•-  ^-=^--=--=-4^^.-=.-^-=^!^^^^^^^^_-^=^=  =  =^J 

u= 

i 

t4i".                                                6  alt  (S>  IO"=  fe'-O" 

*V' 

2i"                      3'-3i"                              5"                           3'-3^" 

si 

II  15"  "c 

AZ 

*1-5" 

V, 

v> 

CO 

d| 

i 

1 

Open  hole*   £-  4  BEAMS     B  \Z 

FIG.  58^. — Detail  of  an  I-Beam. 

(2)  In    these    shapes,    holes    will    be    drilled    or    punched. 
Longitudinal  spacing  must  be  given  in  all  cases.     If  more  than 


^  GIRDERS    GG 


FIG.  s8e—  Detail  of  a  Plate  Girder. 

three  are  alike,  they  should  not  be  repeated,  3",  3",  3,"  3",  3", 
but  marked  5  at  3//  =  i'~3//.    Rivets  alternately  spaced  on  two 


176  ELEMENTS  OF  STRUCTURAL  DESIGN 

lines  as  seen  in  Fig.  580  and  in  top  view  of  Fig.  58^  are  located 
so  many  alternate  spaces.  Note  that  distances  given  are  not 
the  center  to  center  measurements  but  are  taken  along 
dimension  line  from  one  rivet  to  a  point  opposite  the  next. 

Suppose  now  we  have  an  angle  20  feet  long  with  40  rivets, 
6"  apart.  Assume  first  that  the  angle  goes  in  a  space  just 
2o'-of  "  long.  Over  all  distance  or  two  edge  distances  must 
then  be  marked  "  not  more."  Second,  suppose  piece  is  to  be 
machined  to  be  20  feet  long  when  finished.  Both  ends  are  then 
marked  "  mill,"  both  edge  distances  given,  and  shop  takes  care 
of  it  if  enough  material  is  ordered.  Third,  let  variation  either 
way  of  a  quarter  inch  be  unimportant.  Practice  varies  here, 
two,  one,  or  none  of  the  edge  distances  being  given,  as  it  is  left 
largely  to  the  discretion  of  the  shop  whether  a  piece  should  be 
cut  to  exact  length  or  not. 

This  brings  us  to  the  subject  of  mill  variation,  see  Art.  17. 
Shapes  from  the  mill  do  not  come  exact  length  unless  a  pro- 
hibitory price  is  paid.  The  schedule  of  variation  is  quite 
complicated.  We  will  state  but  one  very  important  item,— 
I-beams  and  channels  may  come  f "  long  or  short.  Hence  we 
detail  them  so  this  uncertainty  will  do  no  harm  and  mark  the 
allowable  variations,  usually  A",  on  each  end,  Fig.  58^.  In 
case  it  is  required  to  mill  the  end  of  an  I-beam  or  channel, 
it  must  be  ordered  long  enough  so  there  will  be  sufficient  metal 
even  if  it  comes  f "  short. 

(j)  Next  transverse  spacing  must  be  given.  For  each  size 
I-beam,  angle,  and  channel,  there  are  certain  standard  spacings 
(see  hand-book).  These  are  determined  by  edge  distance  and 
clearance  for  driving.  In  case  there  is  more  room  than  needed, 
variation  may  be  made  from  the  standard.  However,  this 
should  be  done  only  by  an  experienced  draftsman. 

Fig.  587  shows  how  dimensions  are  given  for  shapes  other 
than  rectangles.  In  I-and  T-beams,  spacing  in  flanges  is  sym- 
metrical. If  dimensions  marked  x  are  given,  it  means  shape  is 
to  be  milled  or  cut  to  this  dimension.  Avoid,  if  possible,  as 
it  is  very  expensive. 

(4)  Cuts  may  be  located  by  three  methods  as  illustrated  in 
Fig.  58£. 

(5)  Bends  are  specified  by  bevels,  by  radius  of  curvature 


THE  ENGINEERING  DEPARTMENT 


177 


and   bevels,   or   by    the    dimensions    of   the   piece   on   which 
it  goes. 

(6)  Overall  and  center  to  center  dimensions  of  finished 
piece  must  be  given.  Distances  between  groups  of  field  rivets 
are  also  important.  Besides  their  convenience  in  the  drawing 
room,  they  are  an  aid  to  the  inspector.  Always  give  back  to  back 
of  angles.  In  case  of  long  members  'with  complicated  spacing, 
locate  intermediate  points  by  a  separate  line  of  dimensions. 


xux  ux          xujx  uix 

FIG.  58/. — Transverse  Spacing  of  Shapes. 


Let  us  take  up  now  the  question  of  assembly  marks.  Sup- 
pose a  job  involves  1000  tons  and  60  sheets  of  drawings.  Cer- 
tain details  exactly  alike  and  forming part  of  pieces'  tc^be  shipped 
occur  on  different  plans,  often  several  times  on  the  same  sheet.: 
These  may  be  handled  in  the  ordinary  way.  or  method  of  assembly 
marks  may  be  used.  The  latter  system  is  about  as  follows: 

Give  all  except  main  members  a  mark.  Those  on  first 
sheet  will  be  ai,  bi,  .  .  .,  aa-i,  abi,  .  .  .,  bai,  bbi,  and  so  on.  If 


FIG.  58g.— Methods  of  Detailing  Cut. 

now  on  sheet  two,  a  part  occurs  which  is  the  same  as  on  one, 
it  is  given  its  old  mark,  ami  for  instance.  Details  not  like  any- 
thing previous  will  be  given  new  ones,  02,  b2,  .  .  .,  aa2,  etc. 
Parts  that  are  alike  have  the  same  mark  and  conversely.  Those 
which  are  right  and  left  must  be  so  designated.  Details  are 
given  where  piece  first  occurs;  elsewhere  only  enough  is  furnished 
for  other  connecting  parts;  except  that  material  is  billed  once 
on  each  sheet  which  contains  it,  thus,  iL,  4"X3"Xf"Xi'-o" 


bmj.     Elsewhere  on  sheet,  it  is  simply  bmj. 
bmj  is  listed  in  every  place  where  it  occurs. 


In  bills  of  material, 
At  the  first  of  these 


178  ELEMENTS  OF  STRUCTURAL  DESIGN 

places,  total  number  of  bmj  is  given.  In  the  templet  room,  the 
workman  who  is  assigned  to  sheet  3  makes  templet;  if  it  occurs 
on  other  sheets,  the  templet  maker  knows  from  its  number  that 
it  has  already  been  taken  care  of.  It  causes  some  additional, 
work  in  the  drawing  room  but  is  economical  and  efficient  in  the 
shop. 

Every  piece  which  is  shipped  must  have  its  mark  for  identifica- 
tion during  erection.  This  should  be  suggestive,  G  for  girder, 
5,  stringer,  and  so  forth.  In  trusses,  joints  are  sometimes 
lettered  Z7o,  Ui,  etc.,  above;  Lo,  LI,  etc.,  below.  Ui  LQ  is  then 
the  endpost.  These  marks  should  be  given  directly  under 
member  and  in  letters  somewhat  larger  than  rest  of  drawing. 
Writer  prefers  the  form, 


5  Girders  Gi4  j 


Among  the  many  other  ways  in  which  it  may  be  written,  we 
mention, 

'.   ,  .     ,  (  3  as  shown  mark  C  1  4^ 

5  Girders  required  -J  °     ,  ,      ,       ,          , 
2  other  hand  mark 


But  every  experienced  man  knows  what  the  first  inscription 
means  and  no  additional  information  is  given  to  pay  for  extra 
space  and  time  consumed  by  the  second. 

To  distinguish  between  assembly  and  shipping  marks, 
observe  that  several  of  the  former  are  riveted  together  to  make 
one  shipping  mark,  and  a  number  of  latter  when  fastened  together 
form  finished  structure. 

Important  points  to  be  borne  in  mind  in  detailing  are  : 

(1)  Dimensions  must  be  accurate  to  i". 

(2)  All  necessary  measurements  must  be  given,  but, 

(3)  Avoid  needless  repetition. 

(4)  Everything  must  be  clear  and  concise. 

(5)  Show  connecting  work  detailed  on  other  sheets  in  red. 
And  in  the  design  of  details, 

(6)  Use  as  few  shapes  as  possible  in  addition   to   those 
employed  for  sections. 


THE  ENGINEERING  DEPARTMENT  179 


Art.  59.    Design  of  Splices  and  Beam  Connections 

The  following  principles  are  important  for  all  joints,  whether 
splice,  riveted  connection,  or  pin  joint: 

(1)  The  joint  should  be  economical  of  material  and  shop- 
work   and   erection,  the  latter  two  factors  being  the  more  im- 
portant. 

(2)  Be  careful  to  make  details  of  sufficient  strength.     Two 
methods  of  computation  are  employed : 

(a)  Make   details    as    strong   or   stronger   than    the  main 
members. 

(b)  Make    details    as    strong    as    stresses.     Sometimes  for 
small  stresses,  specifications  for  minimum  sized  material  make 
much    larger    members    obligatory.     The    difference    between 
(a)  and  (b)  is  then  considerable.     The  author  prefers  to  use 
(a)  when  the  structure  thus  strengthened  is  worth  enough  more 
to  pay  for  the  additional  outlay. 

(3)  Consider  erection  very  carefully. 

(4)  Make  joints  as  rigid  as  possible. 

(5)  Compactness  adds  to  rigidity,  economy,  and  strength. 

(6)  Important  members  should  meet  at  a  point  except  as 
necessary    to    balance    moment    due    to    own    weight.      (See 
Arts.  55  and  56.) 

In  addition  for  riveted  joints. 

(7)  Keep  field  riveting  to  a  minimum  as  already  noted. 
(Art.  49). 

(8)  One  rivet  is  not  enough  and  two  are  too  few  for  important 
work. 

Practice  has  established  a  number  of  conventional  rules 
for  the  computation  of  rivets  which  do  not  accord  with  actual 
conditions.  Nevertheless,  customary  methods  seem  safe  since 
constants  are  derived  from  tests  making  same  assumptions. 
These  are: 

(a)  That  rivets  completely  fill  the  holes;   as  they  are  driven 
hot  and  afterwards  shrink,  this  cannot  be  true. 

(b)  While  considered  to  fill  the  holes,  their  capacity  is  com- 
puted from  the  original  diameters. 

(c)  Although  supposed  to  carry  their  stresses  by  shearing 


180 


ELEMENTS  OF  STRUCTURAL  DESIGN 


and  bearing,  they  actually  hold  by  the  friction  of  the  cooling 
rivet. 

(d)  While  we  neglect  bending,  there  must  be  considerable 
in  the  body  of  the  rivets. 

(e)  In  tension,  stress  is  considered  as  uniformly  distributed 
over  net  area  with   holes  J"  greater   than   nominal   diameter 
of  rivets. 

(/)  Compression    is    considered    as    distributed    uniformly 
over  gross  area  if  rivets  are  driven;   otherwise   over  net  area. 


16000? 


4000, 


Uooo*     'eooo      (izooo 
FIG.  590. — Assumed  Distribution  of  Stress. 

(g)  Shear  is  sometimes  taken  as  distributed  over  net  area 
and  sometimes  as  over  gross;    the  former  seems  more  logical. 
(ti)  That  the  stress  in  a  group  of  rivets  is  uniformly  dis- 
tributed is  far  from  the  truth.    First,  the  end  rivets  of  a  straight 
axial  connection  must  carry  more   than  middle.     If   stresses 
in    rivets    were    equal,   we    would    have 
impossible   conditions,  shown  in  Fig.  590. 
Secondly,  loads  are    often  applied  eccen- 
trically.    Let  us  suppose  a  load  of  24,000 
Ibs.  to  be  applied  to  the  group  of  rivets 
shown  in   Fig.  596.     The  stress  assuming 
equal    distribution    is    now    4000   Ibs.  in 
each  rivet.     Suppose,  however,  that  load 
is  applied  i&"  to  right  of  right  hand  row 
of  rivets.     The  eccentric  application  of  the 
load  now  causes  a  moment  of  24,000-2^  = 
62,oooin.-lbs.     Let  7?  be  the  stress  on  the 
4  outer  rivets;   then  that  on  the  other  two 
will  be  1.12^/3.2,  assuming  stress  to  vary 
as    distance    from    center    of    gravity  of 
group.    The  moment  of  ^R  is  4 -R -3.2  =  12. 8  R.    That  of  the 
other  two  is  2- 1.12- 1.12-^/3. 2  =  o.fjSR.    Total  =  13.6 R  =  62,000. 

^  =  4550  Ibs.  stress  in  outer  rivets. 
i.i2R/$.2  =  1600  Ibs.  stress  in  other  rivets. 
Maximum  will  be   the  resultant  of  4000  and  4550  =  7050  Ibs. 


FIG.  5Q&.— Two  Stresses 
in  a  Connection  Angle. 


THE  ENGINEERING  DEPARTMENT 


181 


Joints  may  be  divided  as  follows : 

(j)  Tension. 

(a)  Splices  (2)  Compression. 

(3)  Bending. 


(b)  Beams  connecting  to  other  pieces. 

Subdivided  according  to  position 
with  regard  to  other  piece. 

(c)  Truss  connections 


(1)  Resting  upon  it. 

(2)  Framing  into  it. 
(j)  Suspended  from  it. 


(1)  Riveted. 

(2)  Pin. 

(c)  Will  be  the  subject  of  the  next  article. 

In  (ai)  and  (02),  it  is  customary  to  splice  by  providing  plates 
on  all  sides,  each  with  not  less  than  two  rows  of  rivets.  For 
the  former,  Fig.  59^,  number  of  rivets  must  be  figured.  In 
the  latter,  Fig.  59^,  we  may  (/)  shear  ends  and  compute  the 


— 

__ 

,  f 

X 

— 

\  f 

3!  c 

• 

ll  f 

i  !  r 

-- 

?  |_t 

HM 

FIG.  5QC. — Splicing  a  Tension  Member.  FIG.  sgd. — Splicing  a  Column. 

necessary  rivets,  (2)  mill  ends  and  put  in  about  two  or  three 
rows  of  rivets  each  side  of  the  joint  as  shown  in  the  figure, 
or  (3)  design  rivets  to  be  as  strong  as  member  hi  bending. 
Common  practice  is  to  use  (2)  and  make  splice  as  near  a  sup- 
port as  connections  will  permit. 

(aj)  Splicing  of  beam  occurs  seldom  except  for  plate  girders, 
under  which  head  it  will  be  taken  up  in  detail.  To  illustrate 
method,  let  it  be  required  to  splice  a  24"  I  at  80  Ibs.  to  conserve 
its  full  net  strength.  See  Fig.  590.  On  each  side,  we  will 
use  a  20" X |"  plate:  7,  gross  =2 50;  7,  net,  estimated  =  175 
in.4  for  each.  I/c  for  a  24"  I  at  80  Ibs.  =7/c  for  splice  =  174.0. 
Estimating  c  at  13.0",  necessary  7  =  2262,  or  1762  must  be 
furnished  by  cover  plates.  Assuming  their  center  of  gravity 
to  be  at  12.5",  A  for  one  flange  is  1762/2 -12.5 '12,5  =  5.65  sq.in. 


182 


ELEMENTS   OF  STRUCTURAL  DESIGN 


Use  two  plates  each  8"Xf",  gross  area  6.00,  net,  4.50  sq.in., 
deducting  2  i"  holes.     This  computation  equates  the  resisting 
moment  of  gross  areas  which  is  only  approximately  correct 
The  rivets  in  this  flange  will  be  in  shear.     To  develop  4.5  sq.in. 
there  will  be  necessary  4.50-1.5,  or  6.75  sq.in.  shearing  area' 


~) 


FIG.  590. — Splicing  a  Beam. 

This  will  mean  12  I"  shop  rivets   on  each   side  of  the  joint  as 
shown. 

Theory  for  rivet  splice  at  -sides  is  similar  to  that  for  riveted 
connections  just  considered.  Here  the  value  R  will  be  that 
for  bearing  and  is  equivalent  to  fXiX  1.5  =0.66  sq.in.  area  for 
flexural  stresses.  1.5  represents  ratio  of  allowable  bearing  to 
bending  if  we  assume  shop  rivets.  In  other  words,  one  rivet 
is  just  as  strong  as  0.66  sq.in.  at  same  point.  0.66(8. 52  +  5. 52 

+  2 . 52)  =  7  2  =  /  f  or  half  row  of  rivets. 
There  will  be  required  350/144  =  3 
rows  of  rivets.  The  correct  de- 
duction for  holes  in  side  plates 
is  2(i).i.(8.52  +  5.52  +  2.52)=8i, 
leaving  net  /  as  169,  substantially 
as  assumed. 

Where  a  beam  rests  on  top  of 
a  piece,  (bi),  it  is  preferably  fast- 
ened thereto  by  holes  through  its 
base.  The  objections  to  this  meth- 
od are, — danger  of  buckling  of 
webs  which  should  be  figured  for 
compression  and,  if  insufficient, 
FIG.  59/.— Suspended  Floor  Beam,  stayed  by  stiffeners;  lack  of  rigidity 

in  beams  which  can  be  prevented 

by  X  bracing  at  each  end;  and  want  of  support  for  piece  to 
which  it  connects. 


THE  ENGINEERING  DEPARTMENT 


183 


(bj)  lacks  rigidity  and  is  now  considered  poor  design.  It 
is  sometimes  seen  in  the  connection  between  the  floor  beams 
and  trusses  of  old  highway  bridges,  Fig.  $gf. 

The   standard   connection,    (62)   is  good.     Fig.    59^   shows 
common  method.     Sometimes  a  "  shelf  angle  "  is  placed  just 
below   the   beam  and   this,   in   con- 
junction with  angles  as  in  figure  or 
an  angle  riveted  onto  top,  forms  an 
acceptable  type.    In  latter  case,  upper 
angle   must  not   be  figured  to  carry 
any  part   of   the  load.      Shelf  angle 
alone  makes  an    inferior  connection 
for   reasons    given  for  (bi) .     When     FIG.  59%.— Beam  Connection, 
beam  connects  to  a  truss    joint,    it 

may  fasten  to  one  of  the  members,  or  to  their  prolongations,  or 
be  riveted  direct  to  the  plate,     (fe)  is  the  common  style. 


Art.  60.    Design  of  Riveted  and  Pin  Joints  in  Trusses 

The  members  of  a  truss  which  meet  at  a  riveted  joint  are 
fastened  together  by  means  of  one  or  two  plates.  The  former 
is  used  for  members  composed  of  one  or  two  angles.  The  latter 
when  connecting  to  I  beam  and  two  channel  sections.  For 
this  case,  distance  between  plates  at  different  joints  should,  if 
possible,  be  made  the  same  and  all  truss  members  arranged  to 
go  outside  or  inside.  For  clearance,  allow  A"  or  £"  if  an 
entering  joint,  Fig.  49^,  is  necessary.  Fastening  plates  to 
one  of  the  pieces  in  the  shop  increases  cost  of  shipping  but 
lessens  field  rivets. 

The  thickness  of  plate  unless  determined  by  connections  is 
preferably  made  such  that  resistance  of  rivets  in  shearing  and 
bearing  are  about  the  same;  however,  it  is  seldom  advisable 
to  make  it  thick  enough  so  material  cannot  be  punched,  Art. 
44.  Its  length  and  breadth  are  determined  by  the  necessary 
number  of  rivets.  Plates  are  often  irregular;  if  material  cut 
from  a  rectangular  plate  will  pay  for  extra  labor  (scrap  is  now, 
1912,  worth  f  cent  per  pound),  it  is  generally  better  to  shear 
it  off.  (Art.  63.) 

Let  us  next  design  joint  shown  in  Fig.  6oa  which  represents 


184 


ELEMENTS  OF  STRUCTURAL  DESIGN 


a  portion  of  a  strain  sheet.  To  get  proper  thickness  of  plates, 
/,  we  will  equate  bearing  and  shearing  values  of  rivet,  assuming 
unit  stress  for  former  to  be  twice  the  latter. 

2  X  Rivet  area  in  bearing  =  Area  in  2  shears,  or, 

or  /  = 
^  =  0.75,  hence  t  =  o.$<)",  use  ft"  plate. 

Assuming  allowable  shearing  and  bearing  values  of  10,000 
and  20,000  Ibs.  per  sq.in.  respectively,  and  for  field  rivets  f  of 


V  rivets 

Max.  Difference  cjoooT 
O 

FIG.  6oa .  — Portion  of  Strain  Sheet. 


FIG.  6ob. — Corresponding  Detail. 


these  amounts,  we  may  prepare  the  following  table  and  then 
design  our  joint  as  shown  in  Fig.  6ob. 


Member. 

Stress. 

Rivet. 

Value. 

No.  Rivets 
Required. 

AB 

48,ooor 

Field 

6330 

8 

BC 

8,iooC 

<  ( 

3310 

3 

CD 

34,3°oC 

<( 

6330 

6 

AD-DO 

67,ooor 

Shop 

8440 

8 

Everything  in  pounds. 
stresses. 


The  last  stress  is  really  the  maximum  difference  of 


PIN  JOINTS 

In  the  other  type,  the  pin  passes  through  the  members 
directly.  Compression  pieces  should  be  designed  to  facilitate 
this.  Tension  members  are  eyebars,  and  as  these  may  be  out 
of  parallel  by  one-eighth  of  an  inch  in  a  foot,  less  difficulty  is 
experienced  in  locating  them.  To  explain  how  "  packing  plan  " 
(a  drawing  showing  arrangement  of  members  around  joints) 
influences  design,  let  us  examine  typical  joints  of  an  ordinary 
Pratt  truss.  Figs.  6oc,  d,  and  e  give  packing  plans  for  hip, 
shoe,  and  a  panel  point  in  the  lower  chord  respectively. 


THE  ENGINEERING  DEPARTMENT 


185 


The  upper  chords  are  made  of  such  width   that  there  is 
room  for  the  diagonals  outside  the  posts.     The  same  position 


FIG.  6oc.— At  Hip. 


Hip  Vertical,  2C5ecKon 


FIG.  6od.— At  Shoe. 


FIG.  6oe. 
At  Lower  Chord. 


FIG.  6oh.  FIG.  6oi. 

Typical  Riveted  Joint.  Typical  Pin  Joint. 

American  Bridge  Co.,  Ambridge,  Pa. 

is  maintained  at  bottom.  The  eyebars  constituting  bottom 
chord  are  passed  outside  the  diagonals  and  inside  end  post. 
Webs  of  latter  should  be  opposite  those  of  shoe. 


186  ELEMENTS  OF  STRUCTURAL  DESIGN 

A  pin  is  treated  as  a  round  beam  acted  upon  by  forces  at 
various  angles.  We  determine,  often  after  several  trials,  which 
loading  or  loadings  stress  the  pin  most;  then  resolve  all 
forces  into  horizontal  and  vertical  components;  find  horizontal, 
vertical,  and  resultant  shear,  and  horizontal,  vertical,  and 
resultant  moment  at  salient  points.  From  maximum  resultant 
shears  and  moments,  proper  size  of  the  pin  may  be  determined 
by  the  usual  rules  of  Applied  Mechanics.  The  second  volume 
of  this  work  will  give  sample  computations. 

Pin  connected  structures  are  easier  to  erect.  Also,  their 
joints  are  more  like  the  hinges  assumed  in  computation,  hence 
cause  smaller  bending  stresses  due  to  deflection.  Riveted 
trusses  deflect  less  and  are  stififer. 


Art.  61.    Shoes* 

Masonry  is  comparatively  weak  and  is  capable  of  bearing 
in  compression  but  a  very  small  part  of  load  carried  by  an 
equal  amount  of  steel.  It  is  therefore  necessary  to  build  out 
at  supports,  and  the  structure  for  this  purpose  is  called  a  shoe. 
It  should  be  capable  of  transmitting  the  following  forces : 

(/)  The  vertical  reaction  from  the  girder  to  the  masonry. 

(2)  A  sidewise  pressure  caused  by  the  wind  or  centrifugal 
force  from  the  bracing  to  the  anchor  bolts. 

(j)  An  uplift  caused  by  wind  from  girder  or  truss  to  nuts 
of  anchor  bolts. 

Short  spans  are  sometimes  fixed  at  both  ends.  The  usual 
case,  however,  is  that  one  end  is  fixed  and  the  other  is  free  to 
move.  For  the  former  it  must  carry: 

(4)  The  longitudinal  force  caused  by  traction  or  applica- 
tion of  the  brakes. 

We  will  next  give  desirable  qualities  for  ideal  shoes.  First, 
for  the  free  end: 

(a)  It  should  move  with  very  little  friction. 

(b)  It  should  be  accessible  for  cleaning,  oiling,  or  repair. 
Next,  for  both  ends: 

(c)  Arrangement  ought  to  be  such  that  bridge  may  be  readily 

*See  Part  III,  "Details  of  Bridge  Construction— Plate  Girders,"  by  Skinner. 


THE  ENGINEERING  DEPARTMENT  187 

detached  from  its  foundation.  As  cinders,  dirt,  and  moisture 
are  likely  to  gather  around  the  shoe,  (b)  and  (c)  need  careful 
attention. 

(d)  Details  should  distribute  pressure  uniformly  either  before 
or  after  deflection. 

The  requirement  (d)  is  usually  ignored  on  short  spans 
although  the  concentration  of  pressure  caused  thereby  on  the 
outside  edge  of  the  masonry  must  be  considerable.  For  longer 
spans,  we  use  the  pin  joint. 

We  shall  classify  as  follows: 

Type  (i)  Fixed  without  phi. 

(2)  Free  without  pin,  sliding  joint. 

(3)  Free  without  pin,  rolling  joint. 

(4)  Fixed  with  pin. 

(5)  Free  with  pin,  rolling  joint. 

Type  (/)  Fixed  without  pin.     (Fig.  610.) 

This  is  used  for  spans  of  less  than  75  feet.  Here  a  sole 
plate,  f  to  i"  thick,  is  countersunk  riveted  to  the  bottom  flange 
and  placed  upon  a  bearing  plate  of  same  thickness  and  dimen- 
sions. Planing  is  not  necessary.  Bolt  holes  about  ij" 
diameter  for  2  anchor  bolts  ii"Xi2"  or  thereabouts  are  pro- 
vided for  fastening  to  the  girder.  In  bridges  built  on  a  grade 
one  of  these  plates  is  planed  to  allow  therefor. 

In  a  bridge  where  stringers  are  used,  at  each  abutment,  a 
shoe  must  be  provided  for  every  stringer  or  else  a  floorbeam 
be  used  at  the  end.  The  latter  method  is  probably  the  better. 
It  makes  all  the  stringers  alike  and  it  cheapens  the  masonry, 
but  it  uses  more  steel,  and  the  connections  of  the  end  floorbeam 
are  often  troublesome. 

The  bearing  plate  may  be  steel  or  cast  iron.  Where  a 
high  shoe  is  required,  it  may  be  made  either  of  several  plates 
riveted  together  or  of  cast  iron,  the  latter  detail  being  more 
frequent.  In  case  the  height  is  much  in  excess  of  2  ins.,  it  is 
usually  made  hollow.  Underneath  the  sole  plate  is  sometimes 
placed  a  sheet  of  lead  and  occasionally  it  is  grouted  up. 

Type  (2) .     Free  without  pin,  sliding  joint. 

One  method  is  to  make  as  shown  in  Fig.  6ia,  the  only  dif- 
ference being  that  both  plates  must  be  planed  on  their  surface 


188 


ELEMENTS  OF  STRUCTURAL  DESIGN 


of  contact  and  the  holes  in  the  sole  plate  instead  of  being  cir- 
cular as  in  the  fixed  bearing  are  slotted  as  shown  in  Fig.  6ib. 
The  distance  e  is  made  equal  to  the  expansion  of  span  for  max- 
imum range  of  temperature.  In  this  locality,  (Pittsburgh) 
—  20  to  120°  F.  are  about  the  extremes.  This  gives  us  a  varia- 
tion of  (140 X. 0000065  =  . 00091) X length.  From  this  is  derived 
an  approximate  rule;  J  in.  for  every  10  feet.  This  allowance  is 
also  supposed  to  cover  inaccuracies  of  fabrication  and  change 
in  length  due  to  deflection. 

The  distance  d  is  made  i"  larger  than  bolt  for  ij"  and 
smaller;  \"  being  added  for  ij"  or  larger.  Holes  where  d  =  i| 
and  e  =  i"  would  be  noted  as,— "Slotted  holes  i|"X2£"." 


I 
Ii 


Section  A  A 
FIG.  6 1 a. — Simple 


FIG.  6ib. 


Section  BB 
FIG.  6 ic.— Notched  Ex- 


Fixed  Bearing.        Slotted  Hole.        pansion  Bearing. 


FIG.  6id. 
Cast  Base. 


Another  method  is  to  notch  a  plate  into  the  flange  or  sole 
plate  of  the  girder  as  shown  in  Fig.  6ic.  The  notch  in  the  flange 
should  exceed  in  length  parallel  to  bridge  projection  in  the 
bearing  plate  by  an  amount  equal  to  e,  Fig.  6ib.  The  plate 
shown  dotted  is  advisable  to  provide  against  uplift.  However, 
it  is  often  omitted. 

Either  type  (/)  or  (2)  may  be  used  in  a  simple  form  for  the 
shoes  of  stringers,  the  slotted  hole  being  the  most  common  detail. 

An  example  of  a  high  cast-iron  base  is  shown  in  Fig.  6id. 
This,  it  will  be  observed  might  serve  equally  well  for  a  fixed 
end,  the  only  difference  being  the  holes  in  the  sole  plate  which 
are  slotted  for  the  free  end  and  round  at  fixed.  Principles 
stated  in  Art.  16  must  be  carefully  followed. 

Bearing  surfaces   for  cast  iron  should  always  be  planed. 


THE  ENGINEERING  DEPARTMENT  189 

Sliding  or  rolling  surfaces  must  be  planed  either  for  steel  or 
cast  iron.  Sole  plates  are  often  omitted  for  short  spans  and 
cheap  work. 

Type  (3).  Free  without  pin,  rolling  joint.  For  spans  over 
say  75  feet,  friction  caused  by  a  sliding  joint  is  too  great  and 
rollers  (Art.  38)  are  substituted.  For  plate  girders  and  small 
trusses  these  are  usually  3  to  5"  diameter  and  circular.  A 
large  proportion  of  this  cylinder  does  no  useful  work  and,  if 
cut  away  as  shown  in  Fig.  6ie,  it  continues  to  act  as  before, 
but  occupies  much  less  room  to  transmit  a  given  pressure. 
At  extremes  of  heat  or  cold,  the  rollers  are  inclined  as  shown  by 
Fig.  610;  by  cutting  out  as  seen  in  Fig.  6i/,  we  have  another 
type  which  admits  of  larger  expansion  for  a  given  distance 
center  to  center,  or  of  closer  spacing  for  a  given  expansion. 


. nnpn  _ 

\ .  i  ®  a a  //  ®  a  ®  /TV 


FIG.  6ie.  FIG.  6i/. 

Segmental  Rollers. 

There  are  two  ways  of  providing  for  requirement  (2),  which 
calls  for  the  transmission  of  forces  acting  horizontally  and  at 
right  angles  to  the  bridge.  The  first  method  is  to  fasten  some 
shape,  usually  an  angle,  on  the  base  plate  so  as  to  bear  against 
the  sole  plate  above  as  shown  in  Fig.  6ij.  If  the  fastening  be 
tap  bolts,  the  shapes  may  be  readily  removed  so  that  the  rollers 
can  be  cleaned,  repaired,  or  oiled.  It  also  helps  to  keep  out 
cinders,  dirt,  and  so  forth. 

In  the  second  method,  a  strip  about  2i"Xi"  is  either  riveted 
on  or  planed  out  from  the  bottom  of  the  sole  plate  and  the 
top  of  the  bearing  plate.  A  corresponding  recess  about  A" 
wider  is  turned  in  the  rollers,  Fig.  382.  It  may  be  made  exactly 
the  same  depth  and  then  count  as  a  part  of  the  rollers  in  the 
computation  for  the  length  required;  or,  what  is  more  common, 
a  clearance  of  say  A"  vertically  may  be  allowed,  but  the 
width  of  the  slot  is  then  considered  to  carry  no  load. 

Some  means  must  be  provided  to  keep  the  rollers  the  proper 
distance  apart  and  parallel.  For  this  purpose,  circular  rollers 


190 


ELEMENTS  OF  STRUCTURAL  DESIGN 


need  but  one  guide  bar  on  each  end.  It  may  be  either  fastened 
to  the  rollers  by  tap  bolts  which  are  loose  in  the  guide  bars  and 
tight  in  the  female  thread  of  the  roller,  Fig.  6ig,  or  the  roller 
may  be  turned  down  to  a  shoulder  and  enough  allowed  to  pro- 
ject beyond  the  guide  bar  to  allow  a  cotter  pin  to  be  inserted 
through  a  hole  drilled  for  the  purpose,  Fig.  6ih.  Sometimes 
these  shoulders  are  cut  off  flush  with  the  edge  of  the  guide  bars 


-Guide  Bar  ^Cotter 

FIG.  6ig.  FIG.  6ih. 

Details  of  Rollers. 


FIG.  6ii. 


and  the  latter  are  fastened  together  by  two  rods  passing  through 
pipes  whose  inside  diameters  are  slightly  larger  than  those  of 
the  rods  between  the  bars,  Fig.  6ii. 

In  the  case- of  segmental  rollers,  it  becomes  necessary  not 
only  to  keep  their  axes,  but  also  their  planed  faces  parallel. 
The  well-nigh  universal  way  of  doing  this  is  shown  in  Fig.  6ie. 
Clearance  between  upper  and  lower  bars  must  be  such  as  to 
allow  the  proper  expansion.  Rollers  are  tap  bolted  to  each  of 
the  guide  bars.  The  former  are  usually  not  less  than  6"  hign 
in  order  to  allow  room  for  two  bars, 


XX  XX  XX 


FIG.  617. 


FIG.  6ik. 


Roller  Bearings. 


Provision  against  uplift  is  frequently  omitted  altogether. 
It  is  best  made,  however,  by  prolonging  the  anchor  bolts  and 
passing  them  through  longitudinally  slotted  holes  in  the  sole 
plate,  or  by  using  Z  bars,  Fig.  6ik,  which  while  allowing  the 
necessary  longitudinal  play  hold  it  securely  against  any  upward 
movement. 

Type  (4).  Fixed  with  pin. 

In  the  bearings  thus  far  considered,  the  deflection  of  the 
girder,  if  originally  true,  concentrates  a  large  part  of  the  pressure 


THE  ENGINEERING  DEPARTMENT 


191 


on  the  bridge  end  of  the  abutment.  This  may  be  prevented 
by  giving  the  girder  a  camber,  that  is,  an  upward  curve  sufficient 
to  make  girder  true  when  fully  loaded.  But  the  pressure  is 
uniformly  distributed  then  only  for  one  loading. 

A  much  better  method  is  to  use  a  pin  bearing.  The  shoe  is 
made  in  three  parts.  The  upper  part  is  firmly  fastened  to  the 
girder  and  has  one  or  more  ribs  arranged  symmetrically  about 
the  center  line  of  the  girder,  a  diagrammatic  view  being  given 
in  Fig.  6 1/,  which  also  shows  the  pin  perpendicular  to  the  plane 
of  the  girder  carrying  the  stress  which  it  receives  to  the  lower 
part.  This  is  generally  much  like  the  upper  portion  and  rests 
directly  on  the  under  surface  which  as  well  as  the  top  surface 
of  the  shoe  should  be  planed.  Transverse  "  diaframs,"  explained 
below,  would  be  necessary  for  shoe  seen  in  Fig.  6i/.  These 


Girder        j 


1 


Pin 


FIG.  6 il. — Pin  Bearing. 


FIG.  6im. — Diafram.     FIG.  6iw. — Gusset. 


are  not  shown  in  drawing.  They  must  be  computed  to  carry 
entire  load  as  shoe  would  otherwise  have  little  capacity.  In 
Dedestal,  they  are  needed  to  stiffen  plate. 

The  breadth  of  the  base  should  be  about  twice  the  distance 
from  the  pin  to  masonry;  if  made  much  larger,  too  much  pres- 
sure will  be  concentrated  on  the  area  directly  under  the  pin; 
if  made  much  smaller,  there  is  danger  of  overturning,  although, 
of  course,  a  great  deal  depends  on  the  structural  arrangement 
for  carrying  these  stresses.  A  base  plate  more  than  18"  in 
largest  dimensions  should  be  not  less  than  f"  thick  and  no 
plate  should  project  more  than  4"  from  a  support  and  these 
supports  should  be  not  more  than  10"  apart.  When  the  ribs 
are  not  sufficient  for  this  purpose,  gussets,  Fig.  6in,  may  be 
built  out  from  them  or  partitions  commonly  called  "  diaframs  " 
or  "  diaphragms,"  Fig.  6iw,  placed  between  them.  Both 


192 


ELEMENTS  OF  STRUCTURAL  DESIGN 


serve  the  important  purpose  of  stiffening  the  ribs.  When  unsup- 
ported, the  thickness  should  be  at  least  one-twelfth  the  length. 

The  pin  is  of  medium  steel  and  should  fasten  both  shoe  and 
pedestal  together  to  prevent  a  possible  uplift,  although  the  pin 
is  often  set  in  two  half  holes. 

The  shoe  and  pedestal  may  be  cast  or  riveted.  In  the 
former  case  it  may  be  cast  iron  or  of  cast  steel,  the  latter  being 
better  but  more  expensive.  The  usual  thickness  of  metal 
is  1 1  or  1 1".  Four  bolts  ij"  diameter  are  common  for  anchor 
bolts. 

Riveted  shoes  can  be  made  lighter  than  cast  shoes  and 
are  less  likely  to  injury  from  impact.  Both  shoe  and  pedestal 


FIG.  6  10.—  Cast-Shoe  of  Type  (4).        FIG.  6  ip—  Riveted  Pedestal  of  Type 


are  composed  of  horizontal  plates  to  which  ribs  parallel  to  plane 
of  girder  or  truss  are  attached  by  means  of  angles.  These 
ribs  are  made  of  one  heavy  plate  or  2  or  3  lighter  ones  riveted 
together  and  are  planed  where  they  bear. 

Diaframs  are  made  of  4  angles  and  a  plate,  Fig.  6iw,while 
gussets  are  composed  of  2  pairs  of  angles  and  a  triangular  plate  , 
Fig.  6in. 

Rivets  in  the  base  plate  of  the  pedestal  should  be  counter- 
sunk. Hence,  as  they  have  scarcely  any  stress,  use  maximum 
allowable  spacing.  The  locking  together  is  accomplished  and  at 
the  same  time  a  minimum  of  stress  put  in  the  pin  by  passing  it 
through  the  outside  plates  of  the  pedestal  and  the  inside  plates 


THE  ENGINEERING  DEPARTMENT  193 

of  the  shoe  as  shown  in  Fig.  6i/.  A  clearance  of  about  f" 
should  be  provided  between  the  plates. 

Type  (5)  Free  with  pin,  rolling  joint. 

This  type  is  made  like  type  (4)  except  the  roller  nests  and 
plates  on  which  it  bears,  which  are  like  type  (j). 


FIG.  6iq. — Typical  Shoe,  Type  (4).     Showing  Two  Shoes  Connected  by  an  End 
Strut,  American  Bridge  Co.,  Ambridge,  Pa. 


Art.  62.    Structural  Drawings 

The  organization  of  a  structural  drawing  room  is  about  as 
follows : 

(z)  Chief  Engineer,  in  general  charge  of  all  engineering 
work,  and  particularly  interested  in  questions  of  design  and 
securing  new  contracts. 

(2)  Head  Draftsman  looks  out  for  the  minor  questions  of 
design,  but  his  duties  are  largely  executive,  allotting  work, 
handling  correspondence,  hiring  and  discharging  men.  He 
should  be  capable  of  encouraging  a  spirit  of  loyalty  in  every 
subordinate. 

(j)  Squad  Bosses  are  placed  in  charge  of  a  group  of  four  to 
twelve  men,  and  report  to  the  head  draftsman.  They  are 
expected  to  do  actual  work  besides  superintending  that  of  the 
other  men. 


194 


ELEMENTS  OF  STRUCTURAL  DESIGN 


(4)  Estimators,  see  Art.  53. 

(5)  Checkers,  see  Art.  66. 

(6)  Detailers  make  the  shop  drawings  from  strain  sheets 
and  write  bills. 

(7)  Tracers  copy  drawings  already  worked  out  in  pencil  or 
write  simple  bills.     They  gradually  take  up  detailing. 

(8)  Stenographers,  blueprint  boys,  errand  boys,  and  so  on. 
The  drawing  is  preferably  made  on  dull  side  of  tracing 

cloth  in  order  to  show  pencil  marks  clearly.  An  experienced 
detailer  will  make  a  drawing  directly  (5n  it.  Parts  of  simple 
structures  may  be  inked  in  direct  if  no  changes  are  likely.  The 
common  and  about  the  best  size  is  24^X^6"  outside  with  one- 
half  inch  border  all  the  way  around.  Sheets  about  io"X 


2O  -O-  c/c 


Riveti  *' 

Open  hole*  }t"  461    ££ 

\2.   BEAM5  4BZ  f* 
4B3 

FIG.  62a. — Detail  of  Several  Kinds  of  a  Beam  on  One  Sketch. 

12"  may  be  used  for  detailing  I  beams,  channels,  andH  sections. 
Often  beam  sketches  with  dimension  lines  are  printed  thereon. 
Clearness  and  neatness  are  essential  qualities  of  a  structural 
drawing.  Use  t"  =  i'  for  large  or  very  simple  work,  and  i"  for 
other  ordinary  cases.  Special  larger  scales  are  employed  only 
for  complicated  details  or  machining.  Where  work  is  of  a 
uniform  nature,  a  break  may  be  inserted  and  only  a  portion  of 
the  length  shown.  Sometimes  center  lines  of  truss  are  made 
to  one  scale  while  details  around  each  joint  are  much  larger. 
Ignore  scale  where  a  clearer  drawing  may  be  secured.  In 
changing  dimensions,  we  seldom  alter  sketch.  Do  not  attempt 
to  crowd  the  drawing.  Of  course,  every  additional  tracing 
means  much  more  blueprinting.  However,  we  believe  that  no 
money  is  gained  by  putting  objects  so  close  together  that 
there  is  not  the  proper  space  between  views  and  the  different 
pieces.  Always  allow  more  room  than  you  think  you  need, 


THE  ENGINEERING  DEPARTMENT  195 

because  changes,  errors,  and  lack  of  foresight  tend  to  increase 
amount  to  be  shown  on  a  drawing. 

In  case  several  pieces  are  somewhat  alike  but  not  exactly 
so,  they  are  detailed  by  one  sketch,  notes  and  separate  sets  of 
dimensions  showing  difference,  Fig.  620.  Notice  carefully  and 
consult  many  other  drawings  because  no  set  of  rules,  nothing 
but  observation  and  practice,  can  make  a  draftsman. 

Always  follow  a  definite  order.  Fig.  626  shows  method  for 
various  views.  Omit  those  that  are  not  necessary.  If  both  ends 
are  alike,  omit  one  end  view;  if  nearly  so,  show  difference  by 
notes.  It  is  better  if  possible  to  place  vertical  members  with  their 
tops  at  the  top  of  the  sheet,  and 
to  draw  horizontal  members  hori- 
zontally. It  is  wise  in  many  cases  . — . 
to  note  "West"  or  "Mark  this 
end  '  Top ' :  for  convenience  in 
erection.  In  case  structure  is 
symmetrical  about  center  line  or  FIG.  626.— Arrangement  of  Views, 
nearly  so,  note  it  thus  and  detail 

left  half.  In  constructing  views,  parts  which  would  obscure 
or  unnecessary  things  which  would  take  too  much  time  are 
often  omitted.  Do  not  shade  except  for  curved  surfaces,  and 
in  general  avoid  artistic  or  decorative  work  except  perhaps  in 
dealing  with  non-technical  men  in  securing  contracts. 

Conventional  signs  are  very  little  used  except  for  rivets. 
Open  holes,  the  rivets  for  which  are  driven  in  the  field,  should 
be  drawn  to  scale  and  blackened.  A  shop  rivet  is  drawn  to 
scale  of  head  and  left  open.  Flattening  the  head  is  shown  by 
small  lines  at  an  angle  of  45°:  inside  the  rivet  if  on  inside  or  far 
side;  outside  if  on  outside  or  near  side.  The  number  of  lines 
show  the  number  of  eighths  of  inches  in  height  of  rivet  head; 
if  countersunk  and  chipped  an  x  is  used  thus: 

Field  rivet,  full  head • 

Shop  rivet,  full  head .. . .  Q 

Field  rivet,  countersunk  and  chipped  far  side,  ® 

Shop  rivet,  flatten  to  |"  near  side.  . Q 

Field  rivet,  flatten  to  f "  both  sides ^ 

FIG.  62c. 


196  ELEMENTS  OF  STRUCTURAL  DESIGN 

A  "  marking  diagram/'  a  small  line  drawing  of  complete 
structure,  is  advisable  in  many  instances.  Members  detailed 
on  drawing  are  shown  heavy  therein.  Small  pieces  which  are 
bolted  to  larger  ones  for  shipment  must  be  so  marked,  Art.  48,  (2). 

The  lines  showing  the  object  whether  broken  or  full  should 
be  of  medium  weight.  If  a  full  even  1'ne  is  not  secured,  the 
ruling  pen  may  be  dull  or  the  tracing  may  need  a  more  thorough 
rubbing  with  pounce  powder.  On  the  other  hand,  dimension 
lines,  center  lines,  and  so  forth,  should  be  made  as  light  as  pos- 
sible to  ink  readily. 


Visible  line,  1/80"  thick 
Invisible  line,  1/80"  thick 
Dimension  line,  very  thin 

Center  line,  very  thin  1 iV»iU — % e_tc_ 

Section  line,  very  thin 


FIG.  62d. 

Draw  these  out  to  indicated  measurements  on  a  piece  of  paper 
and  then  keep  as  near  as  possible  thereto  by  eye.  Uniformity 
and  correctness  of  proportion  are  essential  even  in  dotted 
lines. 

.  The  salient  points  of  lettering  are  execution,  form,  spacing, 
and  general  arrangement.  The  one  idea  is  uniformity.  Better 
a  lettering  which  is  uniformly  poor  than  one  which  is  partly 
good  and  partly  bad. 

(a)  The  work  done  by  a  man  in  tracing  an  ideal  bit  of 
lettering  may  be  termed  his  execution.     Lines  must  not  be 
blotted,  blurred,  or  even  ragged.     For  design  work,  they  are 
made  of  medium  weight.     Here  it  is  of  utmost  importance  that 
width  be  un'form.     Use  a  medium  pointed  pen  which  makes 
proper  weight  without  pressure.     Ruling  pen  must  be  employed 
altogether  or  not  at  all.     Difficulties  encountered  by  a  novice 
are  a  lack  of  steadiness  which  practice  will  generally  correct, 
and  a  blurring  due  to  an  unclean  pen  or  a  partially  dried- 
up  ink. 

(b)  Form.     In  every  system  of  lettering,  there  are  certain 
proportions  which  give  best  results.     Beginners  must  master 
and  use  them.     Furthermore,  we  must  have  uniformity  in: 


THE  ENGINEERING  DEPARTMENT  197 

(1)  Breadth   of   letter.     Do   not   mix   broad    and   narrow 
letters  or  figures.     Except  where  crowded,  make  relative  dimen- 
sions the  same  throughout  the  drawing  and  contract. 

(2)  Height.     Make  same  class  of  letters  same  height  for 
same  job.     For  the  bulk  of  the  work,  heights  should  be:    for 
letters  &  and  f";   whole  numbers,  A";  fractions,  &".      Some 
draftsmen  do  very  well  without  guide  lines,  but  most  men  need 
them.     At  any  rate  adjoining  letters  must  have  equal  heights. 

(j)  Vertical  or  slanting  letters  may  be  used  but  inclination 
must  be  kept  constant  for  same  class  of  lettering  and  particularly 
in  the  same  note  or  line  of  dimensions. 

We  give  below,  first  correct  lettering  and  then  in  turn  errors 
(&),  (i),  (2),  and  0). 

Rivet    Rivet    Rivet     Rivet    /Pivet 

FIG.  626. 

(c)  Spacing  between  letters  of  the  same  word  and  between 
different  words  should  appear  equal.     This  does  not  mean  that 
they  will  be  equal. 

Rivet     not    Rivet 

FIG.  62/. 

(d)  General  arrangement  should  harmonize  with  the  drawing. 
Place  lettering  near  object  to  which  it  refers  but  avoid  crowding 
as  much  as  possible.     For  a  long  object  use  a  long  title  and 
vice  versa. 

Notes  should  state  material,  size  of  rivets,  and  open  holes, 
paint,  and  any  unusual  or  important  point  in  the  specifications. 
They  ought  always  to  be  placed  at  the  same  part  of  the  drawing. 

Title  should  give  name  of  purchaser,  location,  span,  and 
kind  of  structure,  name  of  fabricator,  scale,  date,  when  made 
and  by  whom,  when  checked  and  by  whom,  and  name  of  squad 
boss  in  charge. 

Besides  the  drawings  of  structural  steel,  the  detailer  prepares 
those  for  the  machinery,  bills  of  various  sorts,  and  the  erection 


198  ELEMENTS  OF  STRUCTURAL  DESIGN 

diagram.  The  latter  is  a  large  line  drawing  for  the  use  of  the 
erector  and  checker.  It  gives  principal  dimensions  of  the 
structure,  shows  each  part  in  its  finished  position,  and  states 
any  directions  which  may  be  made  necessary  by  any  peculiarities 
of  design.  It  should  also  have  a  list  of  drawings  with  number 
and  contents. 


Art.  63.    Auxiliaries — Bills  of  Material 

Auxiliary  to  the  drawing  are  the  following  bills: 

Material  Clevis  Nuts 

Eyebars,  Plain  Bent  List 

Eyebars,  Adjustable  Castings 

Pins  and  Accessories  Field  Rivets  and  Bolts 

Pilot  and  Driving  Nuts  Shipping  Bill 

These  are  written  or  lettered  in  ink  on  transparent  paper  so 
that  they  may  be  printed.  At  the  top  is  the  name  of  the  com- 
pany, its  location,  and  so  on,  also  a  blank  for  name  of  pur- 
chaser, his  location,  date,  number  of  sheet,  name  of  draftsman, 
checker,  and  so  forth. 

The  bill  of  material  lists  the  steel  required  and  combines 
it  to  make  the  mill  order.  If  a  logical  procedure  were  followed, 
this  would  be  written  after  details  were  made,  checked,  and 
accepted.  Instead  the  order  is  commonly  written  as  soon  after 
contract  is  signed  as  a  draftsman  can  be  secured.  When  the 
drawings  are  accepted,  enough  material. may  be  on  hand  to  start 
job.  At  any  rate,  valuable  time  has  been  saved,  but  at  an 
increased  cost  in  drawing  room.  Rough  layouts  are  made  to 
determine  length  of  sections  and  details  at  critical  points.  Due 
to  the  hurry  and  the  rough  nature  of  the  work,  errors  are  quite 
probable.  Also  purchaser's  engineer  may  require  changes  that 
affect  order.  If  material  has  not  been  shipped  from  mill,  it 
may  be  changed.  When  done  this  way  two  bills  are  written; 
the  first  a  rough  one  in  pencil,  the  second  a  finished  one  in  ink. 
The  two  mill  orders  must  correspond  except  for  changes. 

The  finished  bill  is  as  follows  omitting  heading, 


THE  ENGINEERING  DEPARTMENT 


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200  ELEMENTS  OF  STRUCTURAL  DESIGN 

At  head  of  mill  order,  write  kind  of  material.  Next  the 
pieces  and  mark  as  shown.  Then  list  main  members  and  after- 
wards details  in  some  definite  order. 

If  a  shape  be  changed,  for  example,  a  6"X6"  angle  sheared 
down  to  6"X5J",  note  should  be  made  under  "  Remarks," 
"Cut  to  6"X5J","  while  order  column  reads  6"X6".  If 
piece  be  bent,  it  is  mentioned  under  the  head  of  "  Remarks." 
Such  material  should  be  ordered  separately  from  the  straight 
stuff  because  former  alone  is  sent  to  the  blacksmith  shop. 
Also  material  bolted  for  shipment  must  be  noted. 

Sketch  plates  are  those  of  irregular  plan  which  are  ordered  exact 
size  from  the  mill.  When  cost  of  rectangular  plate  is  greater  than 
cost  of  sketch  plate  at  10  cents  per  hundred  pounds  additional  price 
plus  value  of  scrap  cut  from  rectangular  plate,  about  J  cent  per 
pound,  sketch  plates  should  be  ordered.  Also  where  plates  are 
too  large  for  shop  shears.  Its  plan  must  then  be  placed  under 
"  Description,"  and  "  Mill  Order  "  marked  "  Sketch  Plate." 

Pieces  planed  on  ends  should  be  ordered  about  \"  long  for 
each  mill;  if  on  flat  sides,  add  TS  to  |"  for  each.  For  plain 
stiffeners,  increase  length  by  J";  if  they  contain  crimps,  add 
\"  for  each  plus  its  depth. 

The  length  of  bent  angles  for  ordering  should  be  computed 
on  center  of  gravity  line.  Several  inches  are  added  to  allow  of 
manipulation  in  the  forge  shop. 

I  beams  and  channels  are  purchased  in  lengths  called  for 
on  the  drawings,  allowance  being  made  for  a  variation  of  f " 
either  way  as  already  explained,  Art.  58.  Bars,  plates,  and 
angles,  less  than  15  feet  long,  are  ordered  in  multiple,  that  is, 
to  be  cut  from  longer  pieces.  The  most  convenient  lengths  are 
about  but  not  much  over  30  feet.  Keep  number  of  items 
down  by  combining  mill  order  for  each  sized  section  as  much  as 
possible.  Do  not  order  lengths  exceeding  limits  published 
in  hand-books  without  consulting  mills.  Try  to  keep  mill  order 
in  even  figures,  never  using  fractions  less  than  quarter  inches. 
If  necessary  to  have  two  rolled  edges,  plates  must  be  marked, 
"  U.M.,"  (universal  mill,  Art.  19);  otherwise  either  U.M.  or 
sheared  plate  may  be  furnished. 

Latticing  should  be  ordered  as  so  many  lineal  feet.  Allow 
for  unused  ends  and  waste  in  cutting. 


THE  ENGINEERING  DEPARTMENT  201 

Structural  companies  carry  steel  in  the  more  common 
sizes  and  some  accumulates  from  errors  and  alterations  in  plans. 
Unless  specifications  for  material  prevent,  use  all  of  this  which 
will  fit,  and  write  "  stock  "  under  "  Order  No." 

Art.  64.    Bills  of  Eyebars,  Pins,  and  Accessories 

In  the  bill  of  eyebars  just  below  the  heading  is  placed  a 
sketch  of  a  short  eyebar,  Fig.  64. 

In  the  above  dimensions,  W  and  T  are  given  by  the  strain 
sheet,  Pi  and  P%  are  made  st"  or  6V"  larger  than  pin  which 
is  computed  as  given  in  Art.  60.  T\  and  T*  are  usually  made  the 
same  as  T,  the  exception  being  where  the  pin  does  not  furnish 
sufficient  bearing.  This  is  usually  safeguarded  by  the  rule  that 
it  shall  be  at  least  \W.  DI  and  Dz  are  determined  from  the 
standard  size  of  dies,  tables  of  which  are  furnished  the  drafts- 
man. These  are  so  made  that  there  is  at  least  30%  excess 
metal  in  a  section  through  the  pin.  See  Art.  43- 

The  length  LI   is  the    center  to  center  of  joints.     Then 


Dl+D2 
Li  H  —    -  =L2  and  LI  +  -         -  gives  L3. 

2  2 

To  obtain  A\  and  A^  compute  gross  area  of  eyebar  outside 
of  the  width  W  running  from  center  to  center  pin  holes.  Add 
10%  to  allow  for  burning  and  waste  and  divide  by  W. 

The  bill  for  adjustable  eyebars  is  similar  to  that  of  the 
usual  fixed  type  except  that  at  one  end  is  an  upset  with  thread 
for  which  length,  diameter,  and  number  of  threads  per  inch 
must  be  given.  One  of  the  threads  must  be  left  handed,  while 
the  other  is  right.  The  turnbuckles  or  sleevenuts  are  specified 
by  calling  for  certain  standard  sizes,  for  which  adjustable  ends 
must  be  fitted.  The  area  left  at  the  root  of  the  thread  must  be 
at  least  30%  in  excess  of  that  in  the  body  of  the  bar.  The 
length  must  be  such  as  to  give  the  turnbuckle  plenty  of  play. 
About  3"  should  be  left  between  the  ends  of  the  eyebars.  Li,  L2, 
Z,3,*and  A  ,  are  taken  from  upset  end  of  bar. 

Similarly  in  the  bill  of  pins  a  sketch  of  pins  and  pin  nuts 
and  the  necessary  dimensions  determined  as  stated  in  Art.  46 


202; 


ELEMENTS   OF  STRUCTURAL  DESIGN 


\ 


S  c 


HB 


x     x 


HS 


THE  ENGINEERING  DEPARTMENT  203 

are  given.    As  in  the  bill  for  eyebars,  material  is  ordered  on  same 
sheet. 

For  pilot  and  driving  nuts,  it  is  simply  necessary  to  call  for 
the  kind  and  give  size  of  pin. 


Art.  65.    Other  Bills 

While  a  clevis  nut  may  be  billed  in  a  manner  similar  to 
eyebars,  it  seems  an  unnecessary  amount  of  trouble  since  they 
are  usually  one  of  several  standard  sizes,  the  only  variation 
being  in  the  size  of  thread,  and  opening  of  jaw.  As  in  turn- 
buckles  and  sleevenuts,  they  must  be  threaded  right  and  left 
on  the  same  member.  The  bent  list  is  a  rough  description  of 
the  work  to  be  done  by  the  blacksmith  shop. 

Castings  may  be  placed  on  sheets  for  purposes  of  filing,  or 
they  may  be  detailed  there  without  placing  upon  drawings  at  all. 

The  shop  takes  care  of  shop  rivets  and  bolts.  Those  which 
are  driven  in  the  field  must  be  listed,  however.  This  is  done 
on  a  bill  which  has  columns  for  number,  location,  diameter, 
grip,  and  length  under  head.  The  latter  exceeds  the  grip 
(thickness  of  metal  grasped  by  rivet)  by  an  amount  sufficient 
to  fill  the  hole  plus  enough  to  make  the  head. 

At  the  end  all  rivets  of  the  same  length  u.h.  (under  head) 
are  summed  up,  and  10%  added,  to  allow  for  errors  and  lost  or 
condemned  rivets.  If  in  a  place  where  extra  rivets  can  be 
readily  obtained,  this  bill  need  not  be  checked;  if  otherwise,  a 
larger  percentage  may  be  added  and  the  list  carefully  reviewed 
For  erection  in  inaccessible  locations,  add  liberally  to  longer 
lengths  of  rivets;  in  an  emergency,  a  few  might  be  cut  down 
with  cold  chisel. 

The  shipping  bill  contains  the  marks  of  all  parts  and  mate- 
rial to  be  shipped.  The  bulk  of  this  is  known  simply  by  its 
marks.  Often  a  rough  description  of  each  piece  is  added  together 
with  a  statement  of  any  pieces  which  may  be  bolted  for  shipment. 


204  ELEMENTS  OF  STRUCTURAL  DESIGN 


Art.  66.     Checking 

After  the  drawings  and  their  accompanying  bills  have  been 
completed,  the  checker  examines  them  thoroughly  and  has  the 
draftsman  correct  the  errors.  He  places  a  small  red  check- 
mark or  dot  just  over  each  correct  word  or  dimension.  Any 
which  are  wrong,  he  encircles  in  ordinary  or  blue  pencil,  writing 
correct  amount.  The  author  prefers  to  cross  mark  the  dimension, 
perhaps  explaining  the  reason  to  the  draftsman,  retaining 
the  correct  figure  in  his  own  note-book.  This  ensures  proper 
re-examination  by  the  detailer,  which  is  often  slighted.  Further- 
more an  ignorant  man  is  likely  to  erase  or  even  change  figures 
in  correcting  the  drawing.  Some  companies  keep  "  field 
checkers,"  who  examine  field  holes  and  field  clearances.  We 
believe  that  it  is  unnecessary  if  precautions  stated  in  this  article 
are  followed. 

Some  men  check  very  roughly,  running  over  the  dimensions 
and  examining  a  few  points  here  and  there.  Others  give  atten- 
tion largely  to  small  matters  which  would  not  amount  to  much 
anyway.  They  are  very  fond  of  changing  dimensions  by  a 
thirty-second  of  an  inch;  as  a  matter  of  fact,  in  their  zeal  for 
extreme  accuracy,  much  more  important  matters  may  escape 
them.  There  is  a  great  deal  of  friction  between  detailer  and 
checker.  Actual  errors  must,  of  course,  be  corrected,  but  the 
trouble  arises  over  the  design  of  the  details.  To  avoid  this : 

(1)  Let  both  detailer  and  checker  consider  the  best  good 
of  their  employer. 

(2)  If  checker  cannot  convince  a  reasonable  detailer  of  the 
wisdom  of  a  change,  it  is  better  to  let  it  go  as  it  is.     If  the 
latter  feels  that  his  work  will  not  be  materially  altered,  he  will 
take  much  more  interest. 

Next  let  us  consider  the  good  checker.  He  seldom  finds  it 
necessary  to  change  dimensions  by  a  thirty-second  of  an  inch. 
In  conference  with  the  draftsman,  he  discusses  minor  errors 
of  design  and  suggests  means  for  avoiding  them  in  the  future. 
They  consider  together  the  more  serious  mistakes  and  the  best 
method  of  correcting  them.  When  cost  of  making  change  in 
drawing  room  equals  or  exceeds  amount  to  be  saved,  he  leaves 


THE  ENGINEERING  DEPARTMENT  205 

it  alone  unless  deficient  in  strength.  He  is  quite  insistent  on 
vital  matters.  No  weak  points,  no  infringement  of  specifica- 
tions, no  impracticable  shop  or  field  work  escapes  him.  Espe- 
cial care  is  taken  with  open  holes  and  field  clearances. 

The  following  system  may  be  used  to  great  advantage.  It 
is  better  to  go  over  the  entire  drawing  or  set  of  drawings 
considering  only  one  point  at  a  time.  Before  finally  signing 
the  drawing,  be  sure  that  every  word  and  dimension  is  check 
marked. 

SCHEDULE  FOR  CHECKING 

(1)  Check  Principal  Dimensions.     Read  correspondence  to 
be  sure  no  changes  have  been  made  by  letter.     Then  check 
principal  dimensions  to  agree  with  purchaser's  drawing  and  also 
any  interdependent  sheets  of  details  already  checked.     Above 
all,  compare  carefully  with  masonry  plan.     Want  of  agreement 
with  this  is  certain  to  cause  trouble.     Be  sure  to  examine  arrow- 
heads at  the  same  time.     The  latter  applies   to  all  dimensions. 

(2)  Check   Agreement   with   Specifications.     If   sizes   were 
given  in  strain  sheets  or  general  plans  formingAa  part  of  con- 
tract, they  should  now  be  compared.     Otherwise,  they  must 
be  designed  from  stresses  or  loads.     In  the  same  way,  each  joint, 
splice,  connection,  and  rivet  spacing  in  built-up  girders,  must 
be  compared  or  thoroughly  tested.     Read  specifications  and  see 
that  every  clause  governing  the  work  is  satisfied.     Particularly : 

(a)  Are  ends  of  columns  milled? 

(b)  Does  thickness  of  material  lie  between  minimum  allowable 
and  maximum  practical?     (Arts.  50  d2,  44.) 

(c)  Rivet  spacing  must  not  exceed  nor  be  less  than  certain 
limits.     (Fig.  47^,  Art.  50*1.) 

}  (d)  Edge  distances  should  lie  within  permissible  values. 
(Art.  50^7.) 

(j)  Views  and  Notes. 

(a)  Are  views  properly  shown? 

(b)  Are  rights  and  lefts  given  where  necessary  and  are 
they  correct  where  stated?     (Art.  40.) 

(c)  If  detailed  as  symmetrical  about  center  line,  is  it  so 
mentioned  and  is  it  true? 


206  ELEMENTS  OF  STRUCTURAL  DESIGN 

(d)  Is  each  necessary  mark  given,  no  two  being  alike? 

(e)  Are  pieces  to  be  bolted  for  shipment  so  designated? 
(Art.  48.) 

(/)  Do  the  remaining  notes  convey  the  correct  information 
concisely? 

(g)  Are  any  other  notes  necessary? 
(ti)  Check  title. 

(4)  Shop  rivets  and  bolts. 

(a)  Is  templet  work  economized?    (Art.  40.) 

(b)  Is  spacing  suitable  for  rack  work?   (  Art.  44.) 

(c)  Can   rivets    and    bolts    be    easily    driven?     Are    rivets 
staggered  where  advisable?   (Art.  47.) 

(5)  Miscellaneous. 

(a)  Have  you  good  shop  clearances? 

(b)  Is  all  material  listed? 

(c)  Are  there  measurements  for  inspectors? 

(d)  Are  enough  dimensions  given? 

(e)  Can  lengths  as  detailed  be  secured  from  mill? 

(6)  Erection. 

(a)  Are  pieces  such  as  to  admit  of  economical  shipment? 
(Art.  48.) 

(b)  Consider    some    easy   method    by   which    structure    as 
detailed  could  be  put  together.     (Art.  49.) 

(c)  Check  every  piece  to  conform  to  this  method. 

(d)  Test   clearances   during   and    after   erection.     Do    this 
on  each  connecting  piece,  thus  reviewing  it  at  least  twice. 

(e)  Can  it  be  painted  after  erection? 

(7)  General. 

We  may  now  proceed  to  check  lines  of  dimensions  and  see 
that  they  add  up.  Field  holes  should  receive  special  attention 
and,  like  field  clearances,  be  verified  every  place  where  they 
occur.  For  each  group  check, 

(a)  Vertical  position  and  spacing. 

(b)  Horizontal  position  and  spacing. 

(c)  Arrangement,  how  staggered. 

(d)  Diameter  of  holes. 


THE  ENGINEERING  DEPARTMENT  207 

(8)  Bills. 

Bill  of  rivets  need  not  be  checked  when  located  where  same 
may  be  readily  purchased.  Omit  also  the  reviewing  of  shipping 
bills  for  jobs  in  the  vicinity.  Other  bills  must  be  checked. 
Use  above  outline  where  it  will  apply  but  in  general  these  bills 
are  simply  listing.  Ensure  that  everything  is  taken  off  by 
following  your  own  procedure. 

Above  method  is  rather  slow  but  in  competent  hands  will 
obviate  field  checking  and  lessen  bill  for  field  extras.  The 
latter  is  a  statement  of  extra  cost  during  erection  caused  by 
mistakes  in  drawing  room  and  shop. 

Art.  67.     Other  Steps 

After  the  drawing  is  signed  by  the  checker,  the  squad  boss 
takes  it  to  the  head  draftsman  or  chief  engineer  of  the  structural 
company,  who  examines  the  drawing,  usually  confining  his 
criticism  to  matters  of  strength  and  shopwork.  After  his 
approval,  the  drawings  are  sent,  usually  all  or  a  large  part  of 
a  contract  at  a  time,  to  the  engineer  of  the  purchaser.  His 
examination  is  particularly  for  strength.  If  his  concern  does 
the  erecting,  he  should  investigate  field  connections  and  clear- 
ances; for,  although  the  specifications  frequently  contain 
clauses  making  the  seller  responsible  for  any  errors,  it  is  better 
for  both  parties  that  they  should  be  discovered  in  time.  If  the  job 
is  for  a  lump  sum,  he  is  careful  that  details  are  not  skimped; 
if  for  a  pound  price,  he  guards  against  an  excess  of  material. 
Changes  ordered  by  either  engineer  are  promptly  made.  Extreme 
care  must  be  taken  to  see  that  everything  affected  is  correctly 
altered. 

As  soon  as  both  signatures  are  attached,  blueprints  are 
taken  of  all  the  drawings  and  bills.  As  each  part  of  the  works 
will  need  a  print,  from  10  to  20  copies  of  each  must  be  taken. 
Any  alteration,  whether  caused  by  error  or  by  a  change  in  design, 
must  be  corrected  on  the  tracing  and  date  noted  in  the  title. 
Either  all  the  prints  which  have  been  sent  out  must  be  called 
in  and  destroyed  and  a  new  set  made  from  the  revised  tracing, 
or  else  "  change  slips  "  must  be  sent  out  to  be  pinned  on  the 
drawing.  These  give  the  alteration  to  be  made  and  date  and 


208  ELEMENTS  OF  STRUCTURAL  DESIGN 

name  of  checker.     They  are  regarded  in  much  the  same  light 
as  notices  from  the  registrar's  office  at  a  university. 

Art.  68.  .Examination  of  Structures  in  Use 

When  called  upon  to  examine  a  structure,   the  engineer 
should  obtain  the  following  data: 
(/)  General  dimensions. 
(2)  Cross  sections  of  members, 
(j)  Details  of  these  members. 

(4)  Connections  at  joints. 

(5)  Accessories,  such  as  flooring,  ballast,  etc. 

Preceding  information  may  sometimes  be  obtained  from 
drawings.  Very  great  care  must  be  taken  not  to  use  proposed 
plans  and  even  working  details  are  likely  to  have  been  modified 
during  or  after  construction.  Often  no  trustworthy  data  can 
be  found  and  complete  measurements  must  be  had  if  possible. 

(6)  Character  of  material. 

(7)  Deterioration  through  rot,  rust,  or  other  causes. 

(8)  Wear  caused  by  traffic. 
(g)  Workmanship. 

Number  (6)  may  be  found  on  plans,  or  material  taken  from  a 
part  of  the  bridge  may  be  placed  in  a  testing  machine.  The 
latter  is  the  approved  method  of  determining  injury  caused  by 
fire  or  an  accident  of  some  kind.  (7)  is  obtained  for  steel  by 
scratching  off  rust  and  comparing  former  and  present  thickness. 
The  condition  of  timber  may  be  well  tested  by  boring  a  hole  in 
a  position  where  it  will  least  weaken  the  piece.  (8)  may  be 
very  easy  to  see  as  in  the  planking  of  a  highway  bridge  or  very 
difficult  as  in  the  shank  of  rivets.  In  general  the  wear  of  struc- 
tural work  or  its  overload  is  hard  to  detect  by  visual  examina- 
tion. Loosened  rivets  and  excessive  deflection  are  common 
signs.  Stresses  near  or  beyond  the  elastic  limit  result  in  those 
manifestations  familiar  to  all — necking  down  in  tension  and 
bending  in  compression.  And  finally: 

(10)  Loads  to  which  the  structure  will  be  subjected. 

Taking  now  a  standard  set  of  specifications,  compute 
permissible  stress  in  weakest  part  of  each  member.  Allowance 
must  be  made  for  deterioration,  wear,  or  poor  workmanship. 


THE  ENGINEERING  DEPARTMENT  209 

if  such  be  present.  Now  compare  this  with  actual  total  stress. 
If  excess  of  latter  over  former  be  less  than  10%,  it  is  all  right; 
10  to  20%,  it  needs  close  supervision;  20  to  40%,  is  dangerous; 
above  40%,  must  be  replaced  at  once.  Of  course,  these  are 
general  rules  to  be  used  with  judgment.  Carefully  consider 
such  points  as  efficiency  of  supervision,  loss  of  life,  limb  or 
property,  in  case  of  accident,  and  probability  of  occurrence 
of  maximum  load. 

Art.  69.    Failures 

Space  will  not  permit  us  to  discuss  all  prominent  structural 
failures.  We  shall  take  up  only  a  few  which  will  be  instructive. 
One  purpose  is  to  give  the  young  designer  a  proper  apprecia- 
tion of  the  responsibility  which  he  bears. 

We  think  the  record  is  not  a  bad  one  when  considered  as  a 
proportion.  Furthermore,  the  continual  changes  in  the  art  of 
bridge  building  have  deprived  us  of  the  light  of  experience. 
Pressure  for  extreme  economy  in  engineering,  material,  and 
construction  have  made  very  narrow  margin  for  the  designer. 
What  wonder  if  the  bounds  are  overstepped  at  times?  Such  was 
the  cause  of  the  disaster  to  the  Quebec  bridge,  the  most  important 
of  recent  times.* 

This  structure,  Fig.  6ga,  was  a  cantilever  span  across  the  St. 
Lawrence  River,  with  two  anchor  arms  of  500  feet,  two  cantilever 
arms  of  562.5  feet,  and  one  suspended  span  of  675  feet.  The 
latter  two  made  distance  between  piers  1800  feet,  90  feet  longer 
than  the  Forth  Bridge,  the  longest  existing  span.  The  Quebec 
Bridge  was  67  feet  center  to  center  of  trusses  and  had  a  max- 
imum depth  of  315  feet.  It  was  intended  for  two  railway 
tracks,  two  electric  car  tracks,  two  roadways,  and  two  foot- 
ways. While  building  out  as  a  cantilever  beam,  Aug.  29,  1907, 
it  fell  into  the  river,  150  feet  below,  Fig.  69^.  Seventy-four 
lives  and  two  million  dollars  were  lost. 

The  causes  were:  Assumed  dead  load  was  only  about  75% 
of  the  actual,  too  high  stresses  were  allowed,  and,  by  far  the 
most  important,  insufficient  latticing  was  provided  for  com- 
pression members.  The  lattice  bars  of  a  bottom  chord  member, 

*  See  Engineering  News,  September  5,  1907,  et  seq. 


210 


ELEMENTS  OF  STRUCTURAL  DESIGN 


FIG.  6ga. — Quebec  Cantilever  Bridge  before  its  Fall. 


FIG.  696.— Wreck  of  the  Quebec  Bridge. 


THE  ENGINEERING  DEPARTMENT  211 

Fig.  565,  broke  when  its  stress  was  14,000,000  Ibs.,  or  17,900 
Ibs.  per  sq.in.  This  and  other  columns  in  the  vicinity  suffering 
about  the  same  unit  stress  had  been  showing  signs  of  overload. 
Tests  on  a  model  post,  one- third  size,  showed  an  ultimate  com- 
pressive  strength  of  22,000  Ibs.  per  sq.in.  A  better  latticed  but 
somewhat  similar  column  bent  in  body  at  30,000  Ibs.  per  sq.in. 
In  other  words,  the  compression  strength  of  large  pieces  of  good 
design  is  not  far  from  25,000  pounds  per  square  inch. 

We  may  divide  failures  into  two  classes,  those  which  result 
from: 

(/)  Some  fault  of  design  or  maintenance,  and 

(2)  A  very  unusual  occurrence.  Such  are  earthquakes, 
extreme  storms,  or  floods,  derailment  or  collision  on  a  bridge. 
Provision  can  be  made  for  these  accidents  and  sometimes  this 
is  done.  However,  generally  speaking,  one  is  not  justified  in 
spending  money  for  remote  contingencies. 

We  may  further  subdivide  (i) : 

(id)  Ignorance.     Such  was  the  case  in  the  disaster  which 
occurred  on  the  Boston  and  Albany  Railroad  at  Chester,  Mass., 
in  1893.*     Here  were  located  two  through  skew  spans,  each  of 
riveted  quadruple  latticed  trusses.     Workmen 
were  strengthening  the  bridge  by  placing  addi- 
tional  cover  plates  oh  top  chord,  Fig.  6qc.     To 
do  this,  old  rivets  were  driven  out,  replaced  by 
bolts,  the  plates  added,  and  rivets   substituted  FIG   6  c_sectjon 
for  bolts,  a  few  at  a  time.     The  foreman  does      Of  Top  Chord  of 
not  seem  to  have  fully  appreciated  the  function  of      Chester  Bridge! 
the  rivets  and  allowed  too  many  holes  to  remain 
empty. .  A  train    of  an    engine  and  eight  passenger  cars  was 
passing  over  the  thus  weakened  structure  when  it  broke,  killing 
17  and  injuring  32. 

(ib)  Economy  in  two  forms: 

(ibi)  Saving  in  first  cost  so  extreme  that  failure  results  as 
in  the  Quebec  bridge. 

(162)  Keeping  a  structure  in  service  under  loads  much 
heavier  than  those  for  which  it  was  designed.  The  writer  once 
visited  a  wreck  caused  by  a  mistake  of  this  sort.  As  near  as  he 
can  recollect,  it  was  a  railway  deck  plate  girder  of  65  feet  span. 

*  Engineering  News,  September  7,  1893,  et  seq. 


212  ELEMENTS  OF  STRUCTURAL  DESIGN 

Web  was  5  feet  deep,  made  up  of  36//X3%//X5/-o'/  plates, 
spliced  by  two  bars  and  a  single  row  of  rivets  on  each  side. 
Flanges  were  each  of  2  Ls,  6"X6//XA//  and  2  cover  plates 
14" X A"-  Stiffeners  were  6  to  9  feet  apart. 

(ic)  Lapses. 

We  shall  so  term  cases  where  an  engineer,  otherwise  skillful, 
has  shown  incompetence  or  forgetfulness  in  one  particular 
respect.  As  such  we  shall  class  the  Tay  Bridge  disaster.* 
This  occurred  at  the  Firth  of  Tay  in  Scotland,  Dec.  29,  1879. 
The  structure  was  a  viaduct  about  two  miles  long  and  contained 
85  spans  varying  in  length  from  27  to  245  feet.  The  13  that 
fell  were  through  riveted  lattice  trusses  of  245  feet  span.  They 
were  supported  on  hexagonal  towers  whose  legs  were  of  cast 
iron.  On  the  night  in  question,  a  storm  was  raging  and  the 
wind  was  blowing  against  the  truss  with  a  speed  estimated  at 
72  miles  per  hour.  When  the  engine  with  seven  coaches  had 
almost  reached  the  middle  of  the  thirteen  spans  in  question, 
the  whole  blew  over.  Not  one  of  the  75  persons  on  board  sur- 
vived. The  structure,  otherwise  well  designed,  lacked  strength 
to  resist  wind  stresses.  Failure  was  probably  due  to  weakness 
of  laterals  and  their  connections  by  lugs  to  the  cast-iron  columns. 

(id)  Unforeseen  conditions. 

We  refer  here,  not  to  the  extremely  improbable  conditions 
which  we  have  already  discussed  but  rather  to  those  which  are 
probable  and  should  be  guarded  against. 

Such  a  case  occurred  in  the  Home  building  fire  in  Pittsburgh 
in  May,  1897.!  A  large  part  of  the  damage  was  caused  by  the 
fall  of  a  water  tank  on  the  roof.  This  was  carried  by  naked 
beams  protected  only  by  a  suspended  ceiling  below.  When 
fire  occurred,  it  wrecked  this  ceiling,  and  the  heated  beams 
allowed  tank  to  fall.  Beams  themselves  should  have  been 
fireproofed. 

We  will  give  in  addition  two  more  historic  failures. 

The  Ashtabula  accident  happened  on  the  night  of  Dec.  29, 
18764  The  bridge  was  a  deck,  double  track,  Howe  truss  built 
of  iron.  The  trusses  had  14  panels  at  n  feet,  were  ig'-g" 

*  Engineering  News,  January  3,  1880. 

t  Engineering  Record,  Vol.  XXXV,  p.  537. 

J  Engineering  News,  January  6,  1877  et  seq. 


THE  ENGINEERING  DEPARTMENT  213 

high,  located  if -2"  c.  to  c.  Compression  members  were  each 
made  of  several  small  I  beams  with  practically  nothing  to  cor- 
respond to  modern  latticing,  and  details  were  very  poor.  As  a 
heavy  train  with  two  locomotives  and  eleven  cars  was  passing 
slowly  over  the  bridge,  it  collapsed  just  as  first  engine  had 
nearly  reached  the  other  abutment.  The  train  fell  75  feet  and 
was  consumed  by  fire.  Of  209  persons  on  board,  92  were 
killed  and  64  injured.  It  is  supposed  that  failure  occurred 
in  the  top  chord  under  the  first  locomotive. 

The  Bussey  Bridge  near  Boston,  Mass.,  was  a  skew  bridge 
of  104  feet  span.*  One  truss  was  a  deck  Whipple  of  16  panels 
at  6.5  feet  and  depth  12.5  feet.  Other  was  4  panels  at  26  feet 
and  depth  16  feet.  Pin  through  floorbeam  was  attached  to 
pin  at  hip  joint  by  an  eccentric  loop  welded  hanger  made  of  two 
bars  about  if'Xif'-'.  This  was  improperly  designed  and 
broke,  allowing  latter  part  of  a  long  train  to  fall  through  the 
bridge;  32  were  killed  and  70  hurt. 

We  shall  not  attempt  to  enumerate  the  troubles  of  stand- 
pipes  and  highway  bridges.  Failures  of  the  former  are  frequent 
and  not  always  easy  to  explain.  The  weakness  of  latter  is 
caused  by: 

(a)  The  election  of  politicians  rather  than  business  men  or 
engineers  to  committees  having  the  matter  in  charge. 

(b)  The  tendency  of  the  layman  to  rely  rather  upon  the 
advice  of  salesmen  than  upon  that  of  reputable  designers. 

(c)  Attempts  to  economize.     Except  when  aided  by  experts, 
this  is  very  poor  policy.     Only  a  trained  man  can  tell  whether 
a  low  price  represents  inferior  work  or  not.     Usually  it  does. 

(d)  The  economy  which  precludes  expert  advice,  operates 
in  inspection  of  details  and  field  erection. 

By  far  the  greater  portion  of  accidents  that  have  come 
to  the  author's  attention  have  been  due  to  slowly  applied  or 
quiescent  forces.  Some  of  the  structures  mentioned  above 
had  at  times  carried  rapidly  moving  loads.  However,  the 
failure  did  not  take  place  then  but  later  with  less  impact. 

*  Engineering  News,  March  19,  1887  et  seq. 


INDEX 


A  frame,  120 

Acid  process,  17 

Administration  of  plant,  79 

Allowable  unit  stresses,  134 

Allowable  unit  stresses  in  timber,  n 

Alloys  of  steel,  19 

Angle  block,  69 

Angle  shear,  86 

Angles,  31 

Angles  for  beams,  148 

Angles  for  columns,  161 

Angles  for  tension,  159 

Annealing,  19 

Ash,  ii 

Ashtabula  bridge  disaster,  212 

Assembly,  no 

Assembly  marks,  177 

Assumptions  for  rivets,  179 

Auxiliaries,  198 

Auxiliary  boom,  122 

B 

Bars,  30 

Basic  process,  17 
Bastard  sawed  timber,  24 
Batter  posts,  76 
Beam  connections,  179 
Beam  shears,  85,  104 
Beam  splices,  181 
Beams,  design,  148 
Bearing  blocks,  41 
Beech,  n 
Bending,  104 
Bent  list,  203 


Bents,  trestle,  76 

Bessemer  steel,  16 

Bethlehem  sections,  28,  33,  150 

Bevels,  23 

Bill  of  castings,  203 

Bill  of  clevis  nuts,  203 

Bill  of  eyebars,  201 

Bill  of  material,  198 

Bill  of  rivets,  203 

Bill  of  pins,  201 

Bill,  shipping,  203 

Billing  material,  174 

Boarding,  54 

Boarding,  design  of,  57 

Bolster,  39 

Bolts,  42,  no 

Bolts,  strength  of,  44 

Boring  machines,  92,  96,  108 

Boring  mill,  92,  96,  108 

Box  column,  164 

Box  girder,  151 

Boxing  timber,  12 

Bridges,  67 

Buckle  plates,  105 

Built  I-beams  for  columns,  163 

Bulb  angles,  36 

Bulb  beams,  36 

Burnettizing  timber,  9 

Bussey  bridge  failure,  213 


Camber,  138  f 
Cantilever  traveler,  124 
Caps  for  trestle,  76 
Case  hardening,  6 

215 


216 


INDEX 


Cast  iron,  13,  19 

Castings,  25 

Castings,  steel,  19,  25 

Cedar,  10 

Centrifugal  force,  133 

Change  slips,  207 

Channels,  33,  34 

Channels  for  beams,  148 

Channels  for  columns,  161 

Channels  for  tension  members,  160 

Checking,  204 

Checking  in  timber,  6 

Chester  bridge  failure,  211 

Chestnut,  n,  12 

Chief  Engineer,  193 

Chipping,  94 

Circular  shapes,  29 

Clapboards,  25 

Clearance  for  riveting,  114 

Clearance  diagram,  132 

Clevis  nuts,  107,  203 

Cold  rolling,  28 

Cold  saw,  86,  104 

Cold  shortness,  15 

Color  of  timber,  5 

Column  sections,  35,  161 

Column  splices,  181 

Columns,  design  of,  161 

Columns,  details,  137,  138 

Combination  trusses,  56 

Commercial  shapes  of  timber,  24 

Compressed  air,  82 

Compression  members,  design  of,  161 

Compression    members,    details,    137, 

138,  167 

Computations  for  roof  truss,  57 
Computations  for  bridge,  69 
Connection  plates,  40,  46-49 
Conventional  signs,  195 
Coping  machine,  86,  104 
Corbels,  75 
Cores,  25 
Cornice,  38,  54 
Cost  of  erected  steel,  148 
Cotter,  113 
Cotter  pins,  113 
Countersinking,  116 


Creeper  traveler,  1 24 
Creo-resinate  process,  10 
Creosoting  timber,  8 
Crimping,  105 
Cross  girts,  76 
Cross  shear,  86 
Cypress,  n 

D 

Dapping  ties,  150 

Deck  beams,  36 

Derrick,  120 

Derrick  cars,  122 

Design  in  general,  51,  140 

Design  of  beam  connections,  182 

Design  of  beams,  148 

Design  of  columns,  161 

Design  of  sections,  135 

Design  of  splices,  181 

Design  of  tension  members,  157 

Detailing,  172 

Details  of  columns,  137,  138,  167 

Diaframs,  191 

Dimensions,  23 

Douglas  fir,  10,  12 

Dowel  pins,  42 

Dowels,  42 

Drawings,  194 

Drift  bolts,  42 

Drift  pins,  no 

Drills,  91,  96,  108 

Driving  nuts,  113,  140 

Dry  rot,  7,  38 

Durability  of  timber,  8 


Economical  relations,  143 

Electric  lighting,  82 

End  milling  machine,  94 

Engineering  department,  79 

Entering  joints,  129 

Erection,  80,  119,  139 

Estimating,  146 

Examination  of  structures  in  use,  208 

Executive  department,  79 

Expansion,  138,  188 


INDEX 


217 


Expansion  bolt,  in 
Eyebars,  98,  106 
Eyebars,  bill  of,  201 


Failures,  209 

Falsework,  127 

Field  extras,  207 

Financial  department,  80 

Finishing  pass,  27 

Fins,  27 

Fireproof  timber,  10 

Fish  joint,  43 

Flats,  30 

Flitch  plate  girders,  40 

Floating  method  of  erection,  127 

Floorbeams,  67 

Floorbeams,  computations  for,  70 

Forge  shop,  98 

Foundation  bolts,  in 

Four  angles  as  a  column,  162 

Framing  timber,  53 

Freight  rates,  119 

Fungus  growth,  6 


Gages,  23 

Gallows  frame,  122 

Gang  punch,  90 

Gate  shears,  87 

General  plan,  172 

Gin-pole,  120 

Girder,  box,  151 

Grey  process  of  rolling,  28,  33,  150 

Grip  of  rivet,  116,  135 

Guard  timber,  132 

Gussets,  191 

H 

H-section  for  columns,  161 
H-shape,  36 
Handbooks,  22 
Hangers,  40,  51,  105 
Hard  pine,  10,  12 
Hard  steel,  17 
Haselman  process,  10 
Head  draftsman,  193 


Heart  wood,  3,  12 

Hemlock,  10,  12 

Holder  on,  115 

Hook  bolts,  in 

Home  building  fire, -21 2 

Howe  truss,  67 

Howe  truss,  computations  for,  69 

Hydraulic  jacks,  120 

Hydraulic  pressure,  82 

Hydraulic  riveter,  94 

I 

I-beams,  33 

I-beams  for  beams,  149 
I-beams  for  columns,  161 
I-beams  for  tension  members,  160 
Inhibitors,  20 
Initial  stresses,  19,  26 
Inspection,  117,  208 
Inspection  department,  80 
Iron,  cast,  13 
Iron,  wrought,  15,  19 


Jacks,  hydraulic  120 
Joints,  42,  184 

K 

Keys,  41 
Kiln  drying,  4 
King  post  truss,  62,  66 
Knee  bracing,  54 
Knocked  down,  174 
Knots,  4,  6 
Kyanizing  timber,  9 


Lag  screws,  42 

Lathes,  96 

Lattice  truss,  67 

Latticing,  design  of,  166 

Launching  method  of  erection,  127 

Layout,  84,  100,  109 

Least  work,  65 

Lettering,  196 

Lines,  196 

Linseed  oil,  20 


218 


INDEX 


Loads  for  railroad  bridges,  133 

Lomas  nut,  112 

Long  leaved  Southern  pine,  10,  12 

Loop  rods,  105 

Lumber,  see  Timber. 

Lump  sum,  143 . 

M 

• 

Machine  shop,  95 

Main  shop,  84 

Maple,  ii 

Marine  worms,  7,  8 

Marking  diagram,  196 

Medium  steel,  17,  1 8 

Medullary  rays,  3 

Methods  of  bending  material,  104 

Methods  of  cutting  material,  102 

Methods  of  erection,  119 

Methods  of  making  holes,  108 

Methods  of  riveting,  113 

Methods  of  upsetting,  106 

Metric  system,  22 

Mill  variation,  176 

Milling  machine,  94,  98 

Mortise  and  tenon,  49 

Mouldings,  25 

Multiple  punch,  91,  108 

N 

Nails,  42 
Nickel  steel,  19 
Norway  pine,  10,  12 

O 

Oak,  ii,  12 
Occasional  shapes,  34 
Odor  of  timber,  5 
Offices,  82 
Ogee  washer,  41 
Operating  department,  79 
Order  department,  79 
Oregon  pine,  10,  12 
Organization  of  administration,  79 
Outriggers,  122 
Overrun,  28 


Painting,  118,  139 

Paints,  20 

Parting  lines,  25 

Pattern,  25 

Percussion  riveter,  93 

Phcenix  columns,  35 

Pigment,  20 

Pilot  nuts,  113,  140 

Pin  joints,  184 

Pine,  10,  12 

Pins,  in 

Pins,  bill  of,  201 

Pins,  computations,  186 

Pipes,  36 

Pith  rays,  3 

Planers,  96 

Planing,  25 

Plant,  80 

Plate,  54 

Plate  girders,  economical  depth,  143 

Plate  girders,  erection,  126 

Plate  shears,  86 

Plates,  30 

Pneumatic  drill,  92 

Pneumatic  hydraulic  riveter,  93 

Pneumatic  pressure,  82 

Pneumatic  riveter,  93 

Poplar,  ii 

Portal,  design  of,  72 

Posts  for  trestles,  76 

Power  plant,  82 

Preliminary  plans,  140 

Preservation  of  timber,  8 

Principles  for  cutting  material,  104 

Principles  for  castings,  25 

Principles  of  design  in  wood,  37 

Principles  for  detailing,  178 

Principles  for  dimensioning,  23,  102 

Principles  for  erection,  129 

Principles  for  joints,  1 79 

Principles  for  making  holes,  109 

Principles  for  riveting,  116 

Principles  for  shipping,  119 

Principles  for  templet  making,  101 

Punches,  87 

^Punching,  102,  108,  138 


INDEX 


219 


Purlins,  54 

Purlins,  design  of,  58 


Quarter  sawed  timber,  24 
Quebec  bridge,  165,  209 
Queen  post  truss,  62,  67 

R 

Rack  punch,  90 
Radial  drill,  92,  108 
Rafters,  54 

Rafters,  computation,  58 
Ragged  bolt,  ui 
Rails,  35 
Rare  shapes,  36 
Rat-proofing,  38 
Reaming,  108,  139 
Rectangular  shapes,  30 
Red  shortness,  15 
Re-entrant  cut,  103 
Resonance  of  timber,  5 
Ridge  pole,  54 
Rift  sawed  timber,  24 
Right  and  left,  100 
Rivet  steel,  18 
Riveted  joints,  183 
Riveters,  93 
Riveting,  113 
Rivets,  no,  136-139 
Rods,  29 

Rods  for  tension  members,  158 
Rollers,  98,  189 
Rolling,  27 

Roof  truss,  computations  for,  57 
Roof  truss,  description,  54 
Roofing,  weight,  56 
Rot,  wet  and  dry,  7,  37 
Rotary  planer,  94 
Rounds,  29 


Sales  department,  79 
Sap  wood,  2,  5 
Saw,  86 
Scarf  joint,  43 


Seasoning  timber,  3,  12 
Segmental  rollers,  98,  189 
Segregation,  15 
Separators,  149 
Shakes  in  timber,  5 
Shapers,  96 
Sheared  plate,  30 
Shears,  85,  102 
Sheathing,  54 
Sheathing,  design  of,  57 
Shingles,  13,  25 
Shipment,  118 
Shipping  bill,  203 
Shipping  department,  80 
Shipping  marks,  178 
Shoes,  138,  185,  186 
Shop,  85 

Shrinkage  of  timber,  3,  37 
Sills  for  trestle,  76 
Sizing,  54 

'  Sketch  plates,  200 
Skew  cuts,  103 
Sleeve  nuts,  106 
Slotted,  holes,  109,  188 
Snow,  weight,  56 
Soft  steel,  17,  18 
Spacing  tables,  90. 
Specifications,  131 
Spiegeleisen,  16 
Splice  angles,  36 
Splices,  181 
Split  shears,  86 
Spools,  75 
Spruce,  10,  12 
Squad  bosses,  193 
Squares,  30 
Steel  alloys,  19 
Steel,  Bessemer,  16 
Steel  castings,  19,  25 
Steel,  hard,  17 
Steel,  medium,  17,  j§ 
Steel,  nickel,  19 
Steel,  open  hearth,  17 
Steel,  rivet,  18 
Steel,  soft,  17,  1 8 
Steel,  vanadium,  19 
Stiffeners,  136,  139 


22Q 


INDEX 


Stock  yard,  83 
Straightening  jolls,  83 
Strain  sheet,  172 
Strength  of  timber,  n 
Stringers,  67 
Stringers,  design  of,  70 
Stringers,  for  trestles,  75 
Structural  drawings,  193 
Stud  bolt,  in 
Sub-punching,  199 
S  wedged  bolt,  in 


T-beams,  34 

Table  of  squares,  22 

Tap  bolts,  in 

Tay  bridge  disaster,  212 

Templets,  100, 

Tension  members,  design,  157 

Three  I-beams  for  columns,  163 

Ties,  13,  68,  132 

Timber,  allowable  stresses,  11 

Timber,  color,  5 

Timber,  commercial  shapes  of,  24 

Timber,  durability,  8 

Timber,  faults,  5 

Timber,  fireproofing,  10 

Timber,  grain,  2 

Timber,  growth,  2 

Timber,  knots,  4,  6 

Timber,  odor,  5 

Timber,  preservation,  8 

Timber,  principles  of  design,  37 

Timber,  protection  from  fire,  38 

Timber,  resonance,  5 

Timber,  sap  wood,  2,  5 

Timber,  seasoning,  3 

Timber,  shrinkage,  3 

Timber,  strength,  n 

Timber,  uses  of,  13 

Timber,  varieties,  10 

Timber,  weight,  5 

Toggle  joint  riveter,  93 

Tongued  and  grooved  timber,  25 

Tracers,  194 

Tractive  force,  133 

Traveler,  122 


Traveler,  cantilever,  124 

Traveler,  creeper,  124 

Trestle  bents,  75 

Trough  sections,  35 

Truss  bridges,  erection,  127 

Truss,  weight,  56 

Trussed  beams,  62 

Trusses,  economical  relations,  144 

Turnbuckles,  106 

Turned  bolts,  in,  139 

Two  angles  and  plate  for  columns,  162 

Two  angles  for  columns,  162 

Two  channels  and  I-beam  for  columns, 

1-63 
Two  channels  and  plate  for  columns, 

164 
Two  channels  for  columns,  163 

U 

U-bolt,  in 
Universal  mill,  27 
Upset  ends,  40,  106,  139 
Upsetting,  106 
Uses  of  timber,  13 


Vanadium  steel,  19 
Variation,  mill,  176 
Varieties  of  timber,  10 
Viaducts,  erection,  126 

W 

Wane  in  timber,  6 
Washer  fillers,  112 
Washers,  41,  112 
Water  creosote  process,  10 
Weights  of  roofing,  56 
Weight  of  snow,  56 
Weight  of  timber,  5 
Weight  of  trusses,  56 
Wellhouse  process,  9 
Wet  rot,  timber,  7,  37 
White  pine,  10,  12 
Whitewood,  n 
Wind  pressure,  56,  133 
Wire  drawing,  29 
Wires,  29 


INDEX 


221 


Wood,  see  Timber. 

Wood  fibres,  3 

Wood  screws,  42 

Wooden  bridges,  67 

Workmanship  in  specifications,  138 

Wrought  iron,  15,  19 


X 


X-bracing,  54 


Yellow  pine,  10,  12 

Z 

Zee  bars,  34 
Zee  bars  for  beams,  148 
Zee  bars  for  columns,  161 
Zinc  creosote  process,  9 
Zinc  tannin  process,  9 


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Atkinson,  J.  J.     Friction  of  Air  in  Mines.     (Science  Series  No.  14.) . .  i6mo,  o  50 
Atkinson,  J.  J.,  and  Williams,  Jr.,  E.  H.     Gases  Met  with  in  Coal  Mines. 

(Science  Series  No.  13.) i6mo,  o  50 

Atkinson,  P.     The  Elements  of  Electric  Lighting i2mo,  i  50 

The  Elements  of  Dynamic  Electricity  and  Magnetism i2mo,  2  oo 

Power  Transmitted  by  Electricity i2mo,  2  oo 

Auchincloss,  W.  S.     Link  and  Valve  Motions  Simplified 8vo,  *i  50 

Ayrton,  H.     The  Electric  Arc 1 8vo,  *5  oo 

Bacon,  F.  W.     Treatise  on  the  Richards  Steam-Engine  Indicator  . .  i2mo,  i  oo 

Bailes,  G.  M.     Modern  Mining  Practice.     Five  Volumes 8vo,  each,  350 

Bailey,  R.  D.     The  Brewers'  Analyst 8vo,  *s  oo 

Baker,  A.  L.     Quaternions 8vo,  *i  25 

—  Thick-Lens  Optics (In  Press.) 

Baker,  Benj.     Pressure  of  Earthwork.     (Science  Series  No.  56.)... i6mo, 

Baker,  I.  0.     Levelling.     (Science  Series  No.  91.) i6mo,  o  50 

Baker,  M.  N.     Potable  Water.     (Science  Series  No.  61.) i6mo,  o  50 

—  Sewerage  and  Sewage  Purification.     (Science  Series  No.  i8.)..i6mo,  o  50 

Baker,  T.  T.     Telegraphic  Transmission  of  Photographs i2mc,  *i  25 

Bale,  G.  R.     Modern  Iron  Foundry  Practice.     Two  Volumes.     i2mo. 

Vol.    I.  Foundry  Equipment,  Materials  Used *2  50 

Vol.  II.  Machine  Moulding  and  Moulding  Machines *i  50 

Bale,  M.  P.     Pumps  and  Pumping i2mo,  i  50 

Ball,  R.  S.     Popular  Guide  to  the  Heavens 8vo,  *4  50 

Natural  Sources  of  Power.     (Westminster  Series.) 8vo,  *2  oo 

Ball,  W.  V.     Law  Affecting  Engineers 8vo,  *3  50 

Bankson,  Lloyd.     Slide  Valve  Diagrams.     (Science  Series  No.  108.) .  i6mo,  o  50 

Barba,  J.     Use  of  Steel  for  Constructive  Purposes i2mo,  i  oo 

Barham,  G.  B.    Development  of  the  Incandescent  Electric  Lamp.  .  . .  (In  Press.) 


4        D.  VAN  NOSTRAND   COMPANY'S  SHORT  TITLE   CATALOG 

Barker,  A.    Textiles  and  Their  Manufacture.     (Westminster  Series.).  .8vo,  200 

Barker,  A.  H.     Graphic  Methods  of  Engine  Design i2mo,  *i  50 

Barnard,  F.  A.  P.     Report  on  Machinery  and  Processes  of  the  Industrial 
Arts  and  Apparatus  of  the  Exact  Sciences  at  the  Paris  Universal 

Exposition,  1867 8vo,  5  oo 

Barnard,  J.  H.     The  Naval  Militiaman's  Guide i6mo,  leather  i  25 

Barnard,  Major  J.  G.     Rotary  Motion.     (Science  Series  No.  90.) ....  i6mo,  o  50 

Barrus,  G.  H.     Boiler  Tests 8vo,  *3  oo 

Engine  Tests 8vo,  *4  oo 

The  above  two  purchased  together *6  oo 

Barwise,  S.     The  Purification  of  Sewage i2mo,  3  50 

Baterden,  J.  R.     Timber.     (Westminster  Series.) 8vo,  *2  oo 

Bates,  E.  L.,  and  Charlesworth,  F.     Practical  Mathematics izmo, 

Part   I.    Preliminary  and  Elementary  Course *i  50 

Part  II.    Advanced  Course *i  50 

Beadle,  C.     Chapters  on  Papermaking.     Five  Volumes i2mo,  each,  *2  oo 

Beaumont,  R.     Color  in  Woven  Design 8vo,  *6  oo 

Finishing  of  Textile  Fabrics 8vo,  *4  oo 

Beaumont,  W.  W.     The  Steam-Engine  Indicator 8vo,  2  50 

Bedell,  F.,  and  Pierce,  C.  A.    Direct  and  Alternating  Current  Manual.Svo,  *2  oo 

Beech,  F.     Dyeing  of  Cotton  Fabrics 8vo,  *3  oo 

-  Dyeing  of  Woolen  Fabrics 8vo,  *3  50 

Beckwith,  A.     Pottery 8vo,  paper,  o  60 

Begtrup,  J.     The  Slide  Valve 8vo,  *2  oo 

Beggs,  G.  E.     Stresses  in  Railway  Girders  and  Bridges (In  Press.) 

Bender,  C.  E.     Continuous  Bridges.     (Science  Series  No.  26.) i6mo,  o  50 

—  Proportions  of  Piers  used  in  Bridges.     (Science  Series  No.  4.) 

i6mo,  o  50 

Bennett,  H.  G.     The  Manufacture  of  Leather 8vo,  *4  50 

Bernthsen,    A.      A  Text  -  book  of  Organic  Chemistry.      Trans,   by  G. 

M'Gowan i2mo,  *2  50 

Berry,  W.  J.     Differential  Equations  of  the  First  Species.    i2mo  (In  Preparation.) 
Bersch,  J.     Manufacture  of  Mineral  and  Lake  Pigments.     Trans,  by  A.  C. 


Wright  

8vo, 

*5  oo 

Bertin,  L.  E.     Marine  Boilers.     Trans,  by  L.  S.  Robertson. 

8vo, 

5  oo 

Beveridge,  J.     Papermaker's  Pocket  Book  

I2mo, 

*4  oo 

Binns,  C.  F.     Ceramic  Technology  

8vo, 

*5  oo 

—  Manual  of  Practical  Potting  

8vo, 

*7  50 

TVir  Pnitpr'"?  Crift 

Birchmore,  W.  H.     How  to  Use  a  Gas  Analysis  

i2mo, 

*i  25 

Blaine,  R.  G.     The  Calculus  and  Its  Applications  

i2mo, 

*i  50 

Blake,  W.  H.     Brewers'  Vade  Mecum  

.  ,  8vo, 

*4  oo 

Blake,  W.  P.     Report  upon  the  Precious  Metals  

8vo, 

2    OO 

Bligh,  W.  G.     The  Practical  Design  of  Irrigation  Works.  .  . 

8vo, 

*6  oo 

Blucher,  H.      Modern  Industrial  Chemistry.     Trans,  by  J. 

P.  Millington 

8vo, 

*7  So 

Blyth,  A.  W.     Foods:  Their  Composition  and  Analysis  

8vo, 

7  So 

—  Poisons:  Their  Effects  and  Detection  , 

8vo, 

7  So 

Bockmann,  F.     Celluloid  

i2mo, 

*2  50 

Bodmer,  G.  R.     Hydraulic  Motors  and  Turbines  

i2mo, 

5  oo 

Boileau,  J.  T.     Traverse  Tables  

8vo, 

5  oo 

D.   VAN  NOSTRAND   COMPANY'S  SHORT  TITLE  CATALOG        5 

Bonney,  G.  E.     The  Electro-platers'  Handbook i2mo,  i  20 

Booth,  W.  H.     Water  Softening  and  Treatment 8vo,  *2  50 

—  Superheaters  and  Superheating  and  Their  Control 8vo,  *i  50 

Bottcher,  A.     Cranes:    Their  Construction,  Mechanical  Equipment  and 

Working.     Trans,  by  A.  Tolhausen 4to,  *io  GO 

Bottler,  M.     Modern  Bleaching  Agents.     Trans,  by  C.  Salter i2mo,  *2  50 

Bottone,  S.  R.     Magnetos  for  Au+omobilists 12 mo,  *i  oo 

Boulton,  S.  B.     Preservation  of  Timber.     (Science  Series  No.  82.) .  i6mo,  o  50 

Bourgougnon,  A.     Physical  Problems.     (Science  Series  No.  H3.)..i6mo,  o  50 
Bourry,  E.     Treatise  on  Ceramic  Industries.     Trans,  by  J.  J.  Sudborough. 

8vo,  *s  oo 

Bow,  R.  H.     A  Treatise  on  Bracing 8vo,  i  50 

Bowie,  A.  J.,  Jr.     A  Practical  Treatise  on  Hydraulic  Mining 8vo,  5  oo 

Bowker,  W.  R.     Dynamo,  Motor  and  Switchboard  Circuits 8vo,  *2  50 

Bowles,  0.     Tables  of  Common  Rocks.      (Science  Series  No.  125.).  .i6mo,  050 

Bowser,  E.  A.     Elementary  Treatise  on  Analytic  Geometry i2mo,  i  75 

—  Elementary  Treatise  on  the  Differential  and  Integral  Calculus. i2mo,  2  25 

—  Elementary  Treatise  on  Analytic  Mechanics i2mo,  3  oo 

Elementary  Treatise  on  Hydro-mechanics i2mo,  2  50 

— -  A  Treatise  on  Roofs  and  Bridges i2mo,  *2  25 

Boycott,  G.  W.  M.     Compressed  Air  Work  and  Diving 8vo,  *4  oo 

Bragg,  E.  M.     Marine  Engine  Design i2mo,  *2  oo 

Brainard,  F.  R.     The  Sextant.     (Science  Series  No.  101.) i6mo, 

Brassey;s  Naval  Annual  for  1911 8vo,  *6  oo 

Brew,  W.     Three-Phase  Transmission 8vo,  *2  oo 

Brewer,  R.  W.  A.     The  Motor  Car i2mo,  *2  oo 

Briggs,    R.,    and   Wolff,    A.    R.     Steam-Heating.     (Science    Series   No. 

67.) i6mo,  o  50 

Bright,  C.     The  Life  Story  of  Sir  Charles  Tilson  Bright 8vo,  *4  50 

British  Standard  Sections 8x15  *i  oo 

Complete  list  of  this  series  (45  parts)  sent  on  application. 
Broadfoot,  S.  K.     Motors,  Secondary  Batteries.     (Installation  Manuals 

Series) i2mo,  *o  75 

Broughton,  H.  H.     Electric  Cranes  and  Hoists *9  oo 

Brown,  G.     Healthy  Foundations.     (Science  Series  No.  80.) i6mo,  o  50 

Brown,  H.     Irrigation 8vo,  *5  oo 

Brown,  Wm.  N.     The  Art  of  Enamelling  on  Metal 12 mo,  *i  oo 

Handbook  on  Japanning  and  Enamelling '. i2mo,  *i  50 

—  House  Decorating  and  Painting I2mo,  *i  50 

History  of  Decorative  Art i2mo,  *i  25 

Dipping,  Burnishing,  Lacquering  and  Bronzing  Brass  Ware. . .  i2mo,  *i  oo 

Workshop  Wrinkles 8vo,  *i  oo 

Browne,  R.  E.     Water  Meters.     (Science  Series  No.  81.) i6mo,  o  50 

Bruce,  E.  M.     Pure  Food  Tests i2mo,  *i  25 

Bruhns,  Dr.     New  Manual  of  Logarithms 8vo,  half  morocco,  2  50 

Brunner,   R.     Manufacture   of  Lubricants,   Shoe   Polishes  and  Leather 

Dressings.     Trans,  by  C.  Salter 8vo,  *3  oo 

Buel,  R.  H.     Safety  Valves.     (Science  Series  No.  21.) i6mo,  o  50 

Bulman,  H.  F.,  and  Redmayne,  R.  S.  A.     Colliery  Working  and  Manage- 
ment  8vo,  6  oo 

Burgh,  N.  P.     Modern  Marine  Engineering 4to,  half  morocco,  10  oo 


6       D.  VAN  NOSTRAND   COMPANY'S   SHORT  TITLE  CATALOG 

Burt,  W.  A.     Key  to  the  Solar  Compass i6mo,  leather,  2  50 

Burton,  F.  G.     Engineering  Estimates  and  Cost  Accounts i2mo,  *i  50 

Buskett,  E.  W.     Fire  Assaying nmo,  *i  25 

Cain,  W.     Brief  Course  in  the  Calculus i2mo,  *i  75 

—  Elastic  Arches.     (Science  Series  No.  48.) i6mo,  o  50 

Maximum  Stresses.     (Science  Series  No.  38.) i6mo,  o  50 

Practical  Designing  Retaining  of   Walls.     (Science  Series  No.   3.) 

i6mo,  o  50 

Theory     of     Steel-concrete     Arches    and    of    Vaulted    Structures. 

(Science  Series  No.  42.) i6mo,  o  50 

-  Theory  of  Voussoir  Arches.     (Science  Series  No.  12.) i6mo,  o  50 

Symbolic  Algebra.     (Science  Series  No.  73.) i6mo,  o  50 

Campin,  F.     The  Construction  of  Iron  Roofs 8vo,  2  oo 

Carpenter,  F.  D.     Geographical  Surveying.     (Science  Series  No.  37.) .  i6mo, 

Carpenter,  R.  C.,  and  Diederichs,  H.     Internal  Combustion  Engines. 8vo,  *5  oo 

Carter,  E.  T.     Motive  Power  and  Gearing  for  Electrical  Machinery  .  .8vo,  *5  oo 

Carter,  H.  A.     Ramie  (Rhea),  China  Grass i2mo,  *2  oo 

Carter,  H.  R.     Modern  Flax,  Hemp,  and  Jute  Spinning 8vo,  *3  oo 

Cathcart,  W.  L.     Machine  Design.     Part  I.  Fastenings .8vo,  *3  oo 

Cathcart,  W.  L.,  and  Chaffee,  J.  I.     Elements  of  Graphic  Statics 8vo,  *3  oo 

Short  Course  in  Graphics i2mo,  i  50 

Caven,  R.  M.,  and  Lander,  G.  D.     Systematic  Inorganic  Chemistry .  i2mo,  *2  oo 

Chambers'  Mathematical  Tables 8vo,  i  75 

Charnock,  G.  F.     Workshop  Practice.     (Westminster  Series.) 8vo  (In  Press.) 

Charpentier,  P.     Timber 8vo,  *6  oo 

Chatley,  H.     Principles  and  Designs  of  Aeroplanes.    (Science   Series.) 

No.  126.) i6mo,  o  50 

How  to  Use  Water  Power 1 2mo,  *i  oo 

Child,  C.  T.     The  How  and  Why  of  Electricity i2mo,  i  oo 

Christie,  W.  W.     Boiler- waters,  Scale,  Corrosion,  Foaming 8vo,  *3  oo 

Chimney  Design  and  Theory 8vo,  *3  oo 

Furnace  Draft.     (Science  Series  No.  123.) i6mo,  o  50 

Church's  Laboratory  Guide.     Rewritten  by  Edward  Kinch 8vo,  *2  50 

Clapperton,  G.     Practical  Papermaking 8vo,  2  50 

Clark,  A.  G.    Motor  Car  Engineering.    Vol.  I.    Construction *3  oo 

Clark,  C.  H.     Marine  Gas  Engines i2mo,  *i  50 

Clark,  D.  K.     Rules,  Tables  and  Data  for  Mechanical  Engineers 8vo,  5  oo 

• Fuel:  Its  Combustion  and  Economy i2mo,  i  50 

The  Mechanical  Engineer's  Pocketbook i6mo,  2  oo 

Tramways:  Their  Construction  and  Working 8vo,  7  50 

Clark,  J.  M.     New  System  of  Laying  Out  Railway  Turnouts i2mo,  i  oo 

Clausen-Thue,  W.     ABC  Telegraphic  Code.     Fourth  Edition i2mo,  *s  oo 

Fifth  Edition 8vo,  *7  oo 

—  The  A  i  Telegraphic  Code 8vo,  *7  50 

Cleemann,  T.  M.     The  Railroad  Engineer's  Practice 12 mo,  *i  50 

Clerk,  D.,  and  Idell,  F.  E.     Theory  of  the  Gas  Engine.     (Science  Series 

No.  62.) i6mo,  o  50 

Clevenger,  S.  R.  Treatise  on  the  Method  of  Government  Surveying. 

i6mo,  morocco 2  50 

Clouth,  F.  Rubber,  Gutta-Percha,  and  Balata. 8vo,  *s  oo 


D    VAN  NOSTRAND  COMPANY'S  SHORT  TITLE   CATALOG       7 

Coffin,  J.  H.  C.     Navigation  and  Nautical  Astronomy i2mo,  *3  50 

Colburn,  Z.,  and  Thurston,  R.  H.     Steam  Boiler  Explosions.     (Science 

Series  No.  2.) : i6mo,  o  50 

Cole,  R.  S.    Treatise  on  Photographic  Optics i2mo,  i  50 

Coles- Finch,  W.     Water,  Its  Origin  and  Use 8vo,  *s  oo 

Collins,  J.  E.     Useful  Alloys  and  Memoranda  for  Goldsmiths,  Jewelers. 

i6mo o  50 

Constantine,   E.     Marine   Engineers,    Their   Qualifications   and  Duties. 

8vo,  *2  oo 

Coombs,  H.  A.     Gear  Teeth.     (Science  Series  No.  120.) i6mo,  o  50 

Cooper,  W.  R.     Primary  Batteries 8vo,  *4  oo 

—  "  The  Electrician  "  Primers . . . ' 8vo,  *5  oo 

Part  I *i  50 

Part  II *2  50 

Part  III *2  oo 

Copperthwaite,  W.  C.     Tunnel  Siiields 4to,  *o  oo 

Corey,  H.  T.     Water  Supply  Engineering 8vo  (In  Press.) 

Corfield,  W.  H.     Dwelling  Houses.     (Science  Series  No.  50.) i6mo,  o  50 

-  Water  and  Water-Supply.     (Science  Series  No.  17.) i6mo,  o  50 

Cornwall,  H.  B.     Manual  of  Blow-pipe  Analysis 8vo,  *2  50 

Courtney,  C.  F.     Masonry  Dams 8vo,  3  50 

Cowell,  W.  B.     Pure  Air,  Ozone,  and  Water i2mo,  *2  oo 

Craig,  T.     Motion  of  a  Solid  in  a  Fuel.     (Science  Series  No.  49.) i6mo,  o  50 

—  Wave  and  Vortex  Motion.     (Science  Series  No.  43.) i6mo,  o  50 

Cramp,  W.     Continuous  Current  Machine  Design 8vo,  *2  50 

Crocker,  F.  B.    Electric  Lighting.     Two  Volumes.     8vo. 

Vol.   I.     The  Generating  Plant 3  oo 

Vol.  H.     Distributing  Systems  and  Lamps 3  oo 

Crocker,  F.  B.,  and  Arendt,  M.     Electric  Motors 8vo,  *2  50 

Crocker,  F.  B.,  and  Wheeler,  S.  S.     The  Management  of  Electrical  Ma- 
chinery  i2mo,  *i  oo 

Cross,  C.  F.,  Be  van,  E.  J.,  and  Sindall,  R.  W.     Wood  Pulp  and  Its  Applica- 
tions.    (Westminster  Series.) 8vo,  *2  oo 

Crosskey,  L.  R.     Elementary  Perspective 8vo,  i  oo 

Crosskey,  L.  R.,  and  Thaw,  J.    Advanced  Perspective 8vo,  i  50 

Culley,  J.  L.      Theory  of  Arches.     (Science  Series  No.  87.) i6mo,  o  50 

Davenport,  C.     The  Book.     (Westminster  Series.)  8vo,  *2  oo 

Da  vies,  D.  C.     Metalliferous  Minerals  and  Mining 8vo,  5  oo 

Earthy  Minerals  and  Mining 8vo,  5  oo 

Da  vies,  E.  H.     Machinery  for  Metalliferous  Mines •. 8vo,  8  oo 

Davies,  F.  H.     Electric  Power  and  Traction 8vo,  *2  oo 

Dawson,  P.     Electric  Traction  on  Railways 8vo,  *g  oo 

Day,  C.     The  Indicator  and  Its  Diagrams i2mo,  *2  oo 

Deerr,  N.     Sugar  and  the  Sugar  Cane .* 8vo,  *8  oo 

Deite,  C.     Manual  of  Soapmaking.     Trans,  by  S.  T.  King 4to,  *5  oo 

De  la  Coux,  H.    The  Industrial  Uses  of  Water.     Trans,  by  A.  Morris .  8vo,  *4  50 

Del  Mar,  W.  A.     Electric  Power  Conductors 8vo,  *2  oo 

Denny,  G.  A.     Deep-level  Mines  of  the  Rand 4to,  *io  oo 

Diamond  Drilling  for  Gold *5  oo 

De  Roos,  J.  D.  C.     Linkages.     (Science  Series  No.  47.) i6mo,  o  50 


8        D.  VAN   NOSTRAND   COMPANY'S  SHORT  TITLE  CATALOG 

Derr,  W.  L.     Block  Signal  Operation Oblong  12010,  *i  50 

Desaint,  A.     Three  Hundred  Shades  and  How  to  Mix  Them 8vo,  *io  oo 

De  Varona,  A.     Sewer  Gases.     (Science  Series  No.  55.) i6mo,  o  50 

Devey,  R.  G.     Mill  and  Factory  Wiring.     (Installation  Manuals  Series.) 

i2mo,  *i  oo 

Dibdin,  W.  J.     Public  Lighting  by  Gas  and  Electricity 8vo,  *8  oo 

Purification  of  Sewage  and  Water 870,  6  50 

Dichmann,  Carl.     Basic  Open-Hearth  Steel  Process i2mo,  *3  50 

Dieterich,  K.     Analysis  of  Resins,  Balsams,  and  Gum  Resins 8vo,  *3  oo 

Dinger,  Lieut.  H.  C.     Care  and  Operation  of  Naval  Machinery i2mo,  *2  oo 

Dixon,  D.  B.     Machinist's  and  Steam  Engineer's  Practical  Calculator. 

i6mo,  morocco,  i  25 

Doble,  W.  A.     Power  Plant  Construction  on  the  Pacific  Coast  (In  Press.) 
Dodd,  G.     Dictionary    of   Manufactures,    Mining,    Machinery,    and    the 

Industrial  Arts i2mo,  i  50 

Dorr,  B.  F.     The  Surveyor's  Guide  and  Pocket  Table-book. 

i6mo,  morocco,  2  oo 

Down,  P.  B.     Handy  Copper  Wire  Table i6mo,  *i  oo 

Draper,  C.  H.     Elementary  Text-book  of  Light,  Heat  and  Sound. . .  i2mo,  i  oo 

—  Heat  and  the  Principles  of  Thermo-dynamics i2mo,  i  50 

Duckwall,  E.  W.     Canning  and  Preserving  of  Food  Products 8vo,  *5  oo 

Dumesny,  P.,  and  Noyer,  J.     Wood  Products,  Distillates,  and  Extracts. 

8vo,  *4  50 
Duncan,  W.  G.,  and  Penman,  D.  The  Electrical  Equipment  of  Collieries. 

8vo,  *4  oo 

Duthie,  A.  L.  Decorative  Glass  Processes.  (Westminster  Series.) .  .8vo,  *2  oo 

Dyson,  S.  S.  Practical  Testing  of  Raw  Materials 8vo,  *5  oo 

Dyson,  S.  S.,  and  Clarkson,  S.  S.  Chemical  Works (In  Press.} 

Eccles,  R.  G.,  and  Duckwall,  E.  W.     Food  Preservatives 8vo,  paper  o  50 

Eddy,  H.  T.     Researches  in  Graphical  Statics 8vo,  i  50 

—  Maximum  Stresses  under  Concentrated  Loads 8vo,  i  50 

Edgcumbe,  K.     Industrial  Electrical  Measuring  Instruments 8vo,  *2  50 

Eissler,  M.     The  Metallurgy  of  Gold 8vo,  7  50 

-  The  Hydrometallurgy  of  Copper 8vo,  *4  50 

— —  The  Metallurgy  of  Silver 8vo,  403 

-  The  Metallurgy  of  Argentiferous  Lead 8vo,  503 

—  Cyanide  Process  for  the  Extraction  of  Gold ; 8vo,  3  oo 

—  A  Handbook  on  Modern  Explosives 8vo,  5  oo 

Ekin,  T.  C.     Water  Pipe  and  Sewage  Discharge  Diagrams ;  folio,  *3  oo 

Eliot,  C.  W.,  and  Storer,  F.  H.     Compendious  Manual  of  Qualitative 

Chemical  Analysis i2mo,  *i  25 

Elliot,  Major  G.  H.     European  Light-house  Systems 8vo,  5  oo 

Ennis,  Wm.  D.     Linseed  Oil  and  Other  Seed  Oils 8vo,  *4  oo 

—  Applied  Thermodynamics. 8vo  *4  50 

Flying  Machines  To-day i2mo,  *i  50 

-  Vapors  for  Heat  Engines i2mo,  *i  oo 

Erfurt,  J.     Dyeing  of  Paper  Pulp.     Trans,  by  J.  Hubner 8vo,  *7  50 

Erskine-Murray,  J.     A  Handbook  of  Wireless  Telegraphy 8vo,  *3  50 

Evans,  C.  A.     Macadamized  Roads (In  Press.) 

Ewing,  A.  J.     Magnetic  Induction  in  Iron 8vo,  *4  oo 


D.   VAN   NOSTRAND   COMPANY'S   SHORT  TITLE   CATALOG        9 

Fairie,  J.     Notes  on  Lead  Ores i2mo,  *i  oo 

Notes  on  Pottery  Clays i2mo,  *i  50 

Fairley,  W.,  and  Andre,  Geo.  J.     Ventilation  of  Coal  Mines.     (Science 

Series  No.  58.) i6mo,  o  50 

Fairweather,  W.  C.     Foreign  and  Colonial  Patent  Laws 8vo,  *3  oo 

Fanning,  J.  T.     Hydraulic  and  Water-supply  Engineering 8vo,  *s  oo 

Fauth,  P.      The  Moon  in  Modern   Astronomy.     Trans,  by  J.  McCabe. 

8vo,  *2  oo 

Fay,  I.  W.     The  Coal-tar  Colors 8vo,  *4  oo 

Fernbach,  R.  L.     Glue  and  Gelatine 8vo,  *3  oo 

—  Chemical  Aspects  of  Silk  Manufacture I2mo,  *i  oo 

Fischer,  E.     The  Preparation  of  Organic  Comprwutfte,     T/rvtJ.  by  R.  V. 

Stanford lamfft,  *i   25 

Fish,  J.  C.  L.     Lettering  of  Working  Drawings ')biong  87^,  i  oo 

Fisher,  H.  K.  C.,  and  Darby,  W.  C.     Submarine  Cable  Testing 8vo,  *3  50 

Fiske,  Lieut.  B.  A.     Electricity  in  Theory  and  Practice 8vo,  2  50 

Fleischmann,  W.    The  Book  of  the  Dairy.  Trans,  by  C.  M.  Aikman.   8vo,  4  oo 
Fleming,  J.  A.     The  Alternate-current  Transformer.     Two  Volumes.    8vo. 

Vol.    I.     The  Induction  of  Electric  Currents *5  oo 

Vol.  H.     The  Utilization  of  Induced  Currents *5  oo 

—  Propagation  of  Electric  Currents 8vo,  *3  oo 

—  Centenary  of  the  Electrical  Current 8vo,  *o  50 

—  Electric  Lamps  and  Electric  Lighting 8vo,  *3  oo 

—  Electrical  Laboratory  Notes  and  Forms 410,  *5  oo 

-  A  Handbook  for  the  Electrical  Laboratory  and  Testing  Room.     Two 

Volumes 8vo,  each,  *$  oo 

Fluery,  H.     The  Calculus  Without  Limits  or  Infinitesimals.     Trans,  by 

C.  0.  Mailloux (In  Press.} 

Flynn,  P.  J.     Flow  of  Water.     (Science  Series  No.  84.) i6mo,  o  50 

—  Hydraulic  Tables.     (Science  Series  No.  66.) i6mo,  o  50 

Foley,  N.     British  and  American  Customary  and  Metric  Measures .  .  folio,  *3  oo 
Foster,  H.  A.     Electrical  Engineers'  Pocket-book.     (Sixth  Edition.) 

i2mo,  leather,  5  oo 

—  Engineering  Valuation  of  Public  Utilities  and  Factories 8vo,  *3  oo 

Foster,  Gen.  J.  G.     Submarine  Blasting  in  Boston  (Mass.)  Harbor.. .  .410,  3  50 

Fowle,  F.  F.     Overhead  Transmission  Line  Crossings i2mo,  *i  50 

-  The  Solution  of  Alternating  Current  Problems 8vo  (In  Press.) 

Fox,  W.  G.     Transition  Curves.     (Science  Series  No.  no.) i6mo,  o  50 

Fox,  W.,  and  Thomas,  C.  W.     Practical  Course  in  Mechanical  Draw- 
ing  i2mo,  i  25 

Foye,  J.  C.     Chemical  Problems.     (Science  Series  No.  69.) i6mo,  o  50 

—  Handbook  of  Mineralogy.     (Science  Series  No.  86.) 1 6mo,  o  50 

Francis,  J.  B.     Lowell  Hydraulic  Experiments 4to,  15  oo 

Freudemacher,    P.    W.     Electrical    Mining    Installations.     (Installation 

Manuals  Series  ) i2mo,  *i  oo 

Fritsch,  J.     Manufacture  of  Chemical  Manures.    Trans,  by  D.  Grant. 

8vo,  *4  oo 

Frye,  A.  I.     Civil  Engineers'  Pocket-book 1 2mo,  leather, 

Fuller,  G.  W.      Investigations  into  the  Purification  of  the  Ohio  River. 

4to.*!  *io  oo 

Furnell,  J.     Taints,  Colors,  Oils,  and  Varnishes 8vo,  *i  oo 


10     D.  VAN  NOSTRAND  COMPANY'S  SHORT  TITLE  CATALOG 

Gant,  L.  W.  Elements  of  Electric  Traction 8vo,  *2  50 

Garforth,  W.  E.  Rules  for  Recovering  Coal  Mines  after  Explosions  and 

Fires i2mo,  leather,  i  50 

Gaudard,  J.  Foundations.  (Science  Series  No.  34.) i6mo,  o  50 

Gear,  H.  B.,  and  Williams,  P.  F.  Electric  Central  Station  Distribution 

Systems 8vo,  *3  oo 

Geerligs,  H.  C.  P.  Cane  Sugar  and  Its  Manufacture 8vo,  *s  oo 

Geikie,  J.  Structural  and  Field  Geology 8vo,  *4  oo 

Gerber,  N.  Analysis  of  Milk,  Condensed  Milk,  and  Infants' Milk-Food.  8vo,  i  25 
Gerhard,  W.  P.  Sanitation,  Watersupply  and  Sewage  Disposal  of  Country 

Houses. i2mo,  *2  oo 

Gas  Lighting.  (Science  Series  No.  in.) i6mo,  o  50 

—  Household  Wastes.     (Science  Series  No.  97.) i6mo,  o  50 

— —  House  Drainage.     (Science  Series  No.  63.) i6mo,  o  50 

Sanitary  Drainage  of  Buildings.     (Science  Series  No.  93.) ....  i6mo,  o  50 

Gerhardi,  C.  W.  H.     Electricity  Meters 8vo,  *4  oo 

Geschwind,   L.     Manufacture    of   Alum  and   Sulphates.     Trans,   by   C. 

Salter .8vo,  *s  oo 

Gibbs,  W.  E.     Lighting  by  Acetylene I2mo,  *i  50 

Physics  of  Solids  and  Fluids.     (Carnegie  Technical  School's  Text- 
books.)   *i  50 

Gibson,  A.  H.     Hydraulics  and  Its  Application 8vo,  *5  oo 

Water  Hammer  in  Hydraulic  Pipe  Lines. i2mo,  *2  oo 

Gilbreth,  F.  B.     Motion  Study i2mo,  *2  oo 

—  Primer  of  Scientific  Management. i2mo,  *i  oo 

Gillmore,  Gen.  Q.  A.     Limes,  Hydraulic  Cements  ard  Mortars 8vo,  4  oo 

—  Roads,  Streets,  and  Pavements = i2mo,  2  oo 

Golding,  H.  A.     The  Theta-Phi  Diagram i2mo,  *i  25 

Goldschmidt,  R.     Alternating  Current  Commutator  Motor 8vo,  *3  oo 

Goodchild,  W.     Precious  Stones.     (Westminster  Series.) 8vo,  *2  oo 

Goodeve,  T.  M.     Textbook  on  the  Steam-engine i2mo,  2  oo 

Gore,  G.     Electrolytic  Separation  of  Metals 8vo,  *3  50 

Gould,  E.  S.     Arithmetic  of  the  Steam-engine , i2mo,  i  oo 

—  Calculus.     (Science  Series  No.  112.) i6mo,  o  50 

—  High  Masonry  Dams.     (Science  Series  No.  22.) i6mo,  o  50 

—  Practical  Hydrostatics  and  Hydrostatic  Formulas.     (Science  Series 

No.  117.) i6mo,  o  50 

Grant,  J.     Brewing  and  Distilling.     (Westminster  Series.)  8vo  (In  Press.} 

Gratacap,  L.  P.     A  Popular  Guide  to  Minerals 8vo  (In  Press.) 

Gray,  J.     Electrical  Influence  Machines i2mo,  2  oo 

Greenwood,  E.     Classified  Guide  to  Technical  and  Commercial  Books.  8vo,  *3  oo 

Gregorius,  R.     Mineral  Waxes.     Trans,  by  C.  Salter i2mo,  *3  oo 

Griffiths,  A.  B.     A  Treatise  on  Manures i2mo,  3  oo 

—  Dental  Metallurgy , 8vo,  *3  50 

Gross,  E.     Hops 8vo,  *4  50 

Grossman,  J.     Ammonia  and  Its  Compounds. i2mo,  *i  25 

Groth,  L.  A.     Welding  and  Cutting  Metals  by  Gases  or  Electricity 8vo,  *3  oo 

Grover,  F.     Modern  Gas  and  Oil  Engines 8vo,  *2  oo 

Gruner,  A.     Power-loom  Weaving 8vo,  *3  oo 

Giildrfer,  Hugo.     Internal  Combustion  Engines.     Trans,  by  H.  Diederichs. 

4to,  *io  oo 


D.  VAN   NOSTRAND  COMPANY'S   SHORT  TITLE  CATALOG      11 

Gunther,  C.  O.     Integration i2mo,  *i  25 

Gurden,  R.  L.     Traverse  Tables folio,  half  morocco,  *7  50 

Guy,  A.  E.     Experiments  on  the  Flexure  of  Beams 8vo,  *i  25 

Haeder,    H.      Handbook   on    the    Steam-engine.      Trans,   by   H,  H.  P. 

Powles i2mo,  3  oo 

Hainbach,  R.     Pottery  Decoration.     Trans,  by  C.  Slater i2mo,  *3  oo 

Haenig,  A.    Emery  and  Emery  Industry 8vo, 

Hale,  W.  J.     Calculations  of  General  Chemistry 12 mo,  *i  oo 

Hall,  C.  H.     Chemistry  of  Paints  and  Paint  Vehicles 12 mo,  *2  oo 

Hall,  R.  H.     Governors  and  Governing  Mechanism i2mo,  *2  oo 

Hall,  W.  S.     Elements  of  the  Differential  and  Integral  Calculus 8vo,  *2  25 

—  Descriptive  Geometry 8vo  volume  and  a  4to  atlas,  *3  50 

Haller,  G.  F.,  and  Cunningham,  E.  T.     The  Tesla  Coil I2mo,  *i  25 

Halsey,  F.  A.     Slide  Valve  Gears i2mo,  i  50 

-  The  Use  of  the  Slide  Rule.     (Science  Series  No.  114.) i6mo,  o  50 

-  Worm  and  Spiral  Gearing.     (Science  Series  No.  116.) i6mo,  o  50 

Hamilton,  W.  G.     Useful  Information  for  Railway  Men i6mo,  i  oo 

Hammer,  W.  J.     Radium  and  Other  Radio-active  Substances 8vo,  *i  oo 

Hancock,  H.     Textbook  of  Mechanics  and  Hydrostatics 8vo,  i  50 

Hardy,  E.     Elementary  Principles  of  Graphic  Statics i2mo,  *i  50 

Harrison,  W.  B.     The  Mechanics'  Tool-book i2mo,  i  50 

Hart,  J.  W.     External  Plumbing  Work 8vo,  *3  oo 

Hints  to  Plumbers  on  Joint  Wiping 8vo,  *3  oo 

Principles  of  Hot  Water  Supply 8vo,  *3  oo 

Sanitary  Plumbing  and  Drainage 8vo,  *3  oo 

Haskins,  C.  H.     The  Galvanometer  and  Its  Uses i6mo,  i  50 

Hart,  J.  A.  H.     The  Colorist square  i2mo,  *i  50 

Hausbrand,  E.     Drying  by  Means  of  Air  and  Steam.     Trans,  by   A.  C. 

Wright i2mo,  *2  oo 

Evaporating,  Condensing  and  Cooling  Apparatus.  Trans,  by  A.  C. 

Wright 8vo,  *s  oo 

Hausner,  A.  Manufacture  of  Preserved  Foods  and  Sweetmeats.  Trans. 

by  A.  Morris  and  H.  Robson 8vo,  *3  oo 

Hawke,  W.  H.  Premier  Cipher  Telegraphic  Code 4to,  *5  oo 

—  100,000  Words  Supplement  to  the  Premier  Code 4to,  *5  oo 

Hawkesworth,  J.     Graphical  Handbook  for  Reinforced  Concrete  Design. 

4to,  *2  50 

Hay,  A.     Alternating  Currents 8vo,  *2  50 

—  Electrical  Distributing  Networks  and  Distributing  Lines 8vo,  *3  50 

—  Continuous  Current  Engineering 8vo,  *2  50 

Heap,  Major  D.  P.     Electrical  Appliances '. 8vo,  2  oo 

Heaviside,  0.     Electromagnetic  Theory.     Two  Volumes 8vo,  each,  *5  oo 

Heck,  R.  C.  H.     The  Steam  Engine  and  Turbine 8vo,  *$  oo 

—  Steam-Engine  and  Other  Steam  Motors.     Two  Volumes. 

Vol.    I.     Thermodynamics  and  the  Mechanics 8vo,  *3  50 

Vol.  H.     Form,  Construction,  and  Working 8vo,  *5  oo 

Notes  on  Elementary  Kinematics 8vo,  boards,  *i  oo 

Graphics  of  Machine  Forces 8vo,  boards,  *i  oo 

Hedges,  K.     Modern  Lightning  Conductors 8vo,  3  oo 

Heermann,  P.     Dyers'  Materials.     Trans,  by  A.  C.  Wright i2mo,  *2  50 


12      D.   VAN   NOSTRAND  COMPANY'S   SHORT  TITLE   CATALOG 

Hellot,  Macquer  and  D'Apligny.     Art  of  Dyeing  Wool,  Silk  and  Cotton. 

8vo,  *2  oo 

Henrici,  0.     Skeleton  Structures 8vo,  i  50 

Bering,  D.  W.     Physics  for  College  Students (In  Preparation.} 

Hering-Shaw,  A.     Domestic  Sanitation  and  Plumbing.     Two  Vols. .  .  8vo,  *s  oo 

Elementary  Science 8vo,  *2  oo 

Herrmann,  G.     The  Graphical  Statics  of  Mechanism.     Trans,  by  A.  P. 

Smith i2mo,  2  oo 

Herzfeld,  J.     Testing  of  Yarns  and  Textile  Fabrics 8vo,  *3  50 

Hildebrandt,  A.     Airships,  Past  and  Present 8vo,  *3  53 

Hildenbrand,  B.  W.     Cable-Making.     (Science  Series  No.  32.) i6mo,  o  50 

Hilditch,  T.  P.     A  Concise  History  of  Chemistry i2mo,  *i  25 

Hill,  J.  W.     The  Purification  of  Public  Water  Supplies.      New  Edition. 

(In  Press.) 

• Interpretation  of  Water  Analysis (In  Press.) 

Hiroi,  I.     Plate  Girder  Construction.     (Science  Series  No.  95.) i6mo,  o  50 

Statically-Indeterminate  Stresses i2mo,  *2  oo 

Hirshfeld,  C.  F.     Engineering  Thermodynamics.     (Science  Series  No.  45.) 

i6mo,  o  50 

Hobart,  H.  M.     Heavy  Electrical  Engineering 8vo,  *4  50 

Design  of  Static  Transformers I2mo,  *2  oo 

Electricity 8vo,  *2  oo 

Electric  Trains *. 8vo,  *2  50 

Electric  Propulsion  of  Ships 8vo,  *2  oo 

Hobbs,  W.  R.  P.     The  Arithmetic  of  Electrical  Measurements i2mo,  o  50 

Hoff,  J.  N.     Paint  and  Varnish  Facts  and  Formulas i2ino,  *i  50 

Hoff,  Com.  W.  B.     The  Avoidance  of  Collisions  at  Sea.  .  .  i6mo,  morocco,  o  75 

Hole,  W.     The  Distribution  of  Gas 8vo,  *7  50 

Holley,  A.  L.     Railway  Practice folio,  12  oo 

Holmes,  A.  B.     The  Electric  Light  Popularly  Explained  ....  i2mo,  paper,  o  50 

Hopkins,  N.  M.     Experimental  Electrochemistry 8vo,  *3  oo 

Model  Engines  and  Small  Boats i2mo,  i  25 

Hopkinson,  J.     Shoolbred,  J.  N.,  and  Day,  R.  E.     Dynamic  Electricity. 

(Science  Series  No.  71.) i6mo,  o  50 

Horner,  J.     Engineers'  Turning 8vo,  *3  50 

Metal  Turning i2mo,  i  50 

—  Toothed  Gearing i2mo,  2  25 

Houghton,  C.  E.     The  Elements  of  Mechanics  of  Materials i2mo,  *2  oo 

Houllevigue,  L.     The  Evolution  of  the  Sciences 8vo,  *2  oo 

Howe,  G.     Mathematics  for  the  Practical  Man i2mo,  *i  25 

Howorth,  J.     Repairing  and  Riveting  Glass,  China  and  Earthenware. 

8vo,  paper,  *o  50 

Hubbard,  E.     The  Utilization  of  Wood- waste 8vo,  *2  50 

Humper,  W.     Calculation  of  Strains  in  Girders i2mo,  2  50 

Humphreys,  A.  C.     The  Business  Features  of  Engineering  Practice .  8vo,  *i  25 

Hurst,  G.  H.     Handbook  of  the  Theory  of  Color 8vo,  *2  50 

—  Dictionary  of  Chemicals  and  Raw  Products 8vo,  *3  oo 

—  Lubricating  Oils,  Fats  and  Greases .  .  .  .  : 8vo,  *4  oo 

Soaps 8vo,  *s  oo 

—  Textile  Soaps  and  Oils 8vo,  *2  50 

Hurst,  H.  E.,  and  Lattey,  R.  T.     Text-book  of  Physics 8vo,  *3  oo 


D.   VAN   NOSTRAND   COMPANY'S  SHORT   TITLE  CATALOG      13 

Hutchinson  R.  W.,  Jr.     Long  Distance  Electric  Power  Transmission .  I2mo,  *3  oo 
Hutchinson,  R.  W.,  Jr.,  and  Ihlseng,  M.  C.     Electricity  in  Mining.  .  i2mo, 

(In  Press) 

Hutchinson,  W.  B.     Patents  and  How  to  Make  Money  Out  of  Them.  i2mo,  i  25 

Hutton,  W.  S.     Steam-boiler  Construction 8vo,  6  oo 

• Practical  Engineer's  Handbook 8vo,  7  oa 

-  The  Works'  Manager's  Handbook 8vo,  6  oo 

Hyde,  E.  W.     Skew  Arches.     (Science  Series  No.  15.) •. . .  i6mo,  o  50 

Induction  Coils.     (Science  Series  No.  53.) i6mo,  o  50 

Ingle,  H.     Manual  of  Agricultural  Chemistry 8vo,  *3  oo 

Innes,  C.  H.     Problems  in  Machine  Design i . . .- i2mo,  *2  oo 

Air  Compressors  and  Blowing  Engines i2mo,  *2  oo 

—  Centrifugal  Pumps I2mo,  *2  oo 

The  Fan i2mo,  *2  oo 

Isherwood,  B.  F.     Engineering  Precedents  for  Steam  Machinery 8vo,  2  50 

Ivatts,  E.  B.     Railway  Management  at  Stations 8vo,  *2  50 

Jacob,   A.,  and  Gould,  E.   S.     On  the  Designing  and  Construction  of 

Storage  Reservoirs.     (Science  Series  No.  6.) 1 6mo,  o  50 

Jamieson,  A.     Text  Book  on  Steam  and  Steam  Engines 8vo,  3  oo 

Elementary  Manual  on  Steam  and  the  Steam  Engine i2mo,  i  50 

Jannettaz,  E.     Guide  to  the  Determination  of  Rocks.     Trans,  by  G.  W. 

Plympton i2mo,  i  50 

Jehl,  F.     Manufacture  of  Carbons 8vo,  *4  oo 

Jennings,  A.  S.     Commercial  Paints  and  Painting.     (Westminster  Series.) 

8vo  (In  Press.) 

Jennison,  F.  H.     The  Manufacture  of  Lake  Pigments 8vo,  *3  oo 

Jepson,  G.     Cams  and  the  Principles  of  their  Construction 8vo,  *i  50 

—  Mechanical  Drawing 8vo  (In  Preparation.) 

Jockin,  W.     Arithmetic  of  the  Gold  and  Silversmith 12 mo,  *i  oo 

Johnson,  G.  L.     Photographic  Optics  and  Color  Photography 8vo,  *3  oo 

Johnson,  J.  H.      Arc  Lamps  and  Accessory  Apparatus.     (Installation 

Manuals  Series.) i2mo,  *o  75 

Johnson,    T.    M.      Ship    Wiring    and    Fitting.       (Installation    Manuals 

Series). *o  75 

Johnson,  W.  H.     The  Cultivation  and  Preparation  of  Para  Rubber . . .  8vo,  *3  oo 

Johnson,  W.  McA.     The  Metallurgy  of  Nickel (In  Preparation.) 

Johnston,  J.  F.  W.,  and  Cameron,  C.     Elements  of  Agricultural  Chemistry 

and  Geology i2mo,  2  60 

J°ly>  J-     Raidoactivity  and  Geology i2mo,  *3  oo 

Jones,  H.  C.     Electrical  Nature  of  Matter  and  Radioactivity i2mo,  *2  oo 

Jones,  M.  W.     Testing  Raw  Materials  Used  in  Paint i2mo,  *2  oo 

Jones,  L.,  and  Scard,  F.  I.     Manufacture  of  Cane  Sugar 8vo,  *5  oo 

Joynson,  F.  H.     Designing  and  Construction  of  Machine  Gearing. . .  .8vo,  2  oo 

Jiiptner,  H.  F.  V.     Siderology:  The  Science  of  Iron 8vo,  *5  oo 

Kansas  City  Bridge 4to,  6  oo 

Kapp,  G.     Alternate  Current  Machinery.     (Science  Series  No.  96.) .  i6mo,  o  50 

Electric  Transmission  of  Energy i2mo,  3  50 

Keim,  A.  W.     Prevention  of  Dampness  in  Buildings 8vo,  *2  oo 


14     D.  VAN   NOSTRAND   COMPANY'S  SHORT  TITLE   CATALOG 

Keller,  S.  S.     Mathematics  for  Engineering  Students.     i2mo,  half  leather. 

Algebra  and  Trigonometry,  with  a  Chapter  on  Vectors *i  75 

Special  Algebra  Edition *i  oo 

Plane  and  Solid  Geometry *i  25 

Analytical  Geometry  and  Calculus *2  oo 

Kelsey,  W.  R.     Continuous-current  Dynamos  and  Motors 8vo,  *2  50 

Kemble,  W.  T.,  and  Underbill,  C.  R.     The  Periodic  Law  and  the  Hydrogen 

Spectrum 8vo,  paper,  *o  50 

Kemp,  J.  F.     Handbook  of  Rocks 8vo,  *i  50 

Kendall,  E.     Twelve  Figure  Cipher  Code 4to,  *i$  oo 

Kennedy,  A.  B.  W.,  and  Thurston,  R.  H.     Kinematics  of  Machinery. 

(Science  Series  No.  54.) i6mo,  o  50 

Kennedy,  A.  B.  W.,  Unwin,  W.  C.,  and  Idell,  F.  E.     Compressed  Air. 

(Science  Series  No.  106.) i6mo,  o  50 

Kennedy,  R.     Modern  Engines  and  Power  Generators.     Six  Volumes.   4to,  15  oo 

Single  Volumes each,  3  oo 

Electrical  Installations.     Five  Volumes 4to,  15  oo 

Single  Volumes each,  3  50 

Flying  Machines;  Practice  and  Design i2mo,  *2  oo 

Principles  of  Aeroplane  Construction 8vo,  *i  50 

Kennelly,  A.  E.     Electro-dynamic  Machinery 8vo,  i  50 

Kent,  W.     Strength  of  Materials.     (Science  Series  No.  41.) i6mo,  o  50 

Kershaw,  J.  B.  C.     Fuel,  Water  and  Gas  Analysis 8vo,  *2  50 

Electrometallurgy.     (Westminster  Series.) 8vo,  *2  oo 

The  Electric  Furnace  in  Iron  and  Steel  Production i2mo,  *i  50 

Kinzbrunner,  C.     Alternate  Current  Windings 8vo,  *i  50 

—  Continuous  Current  Armatures 8vo,  *i  50 

Testing  of  Alternating  Current  Machines 8vo,  *2  oo 

Kirkaldy,  W.  G.     David  Kirkaldy's  System  of  Mechanical  Testing 4to,  10  oo 

Kirkbride,  J.     Engraving  for  Illustration 8vo,  *i  50 

Kirkwood,  J.  P.     Filtration  of  River  Waters 4to,  7  50 

Klein,  J.  F.     Design  of  a  High-speed  Steam-engine 8vo,  *5  oo 

Physical  Significance  of  Entropy 8vo,  *i  50 

Kleinhans,  F.  B.     Boiler  Construction 8vo,  3  oo 

Knight,  R.-Adm.  A.  M.     Modern  Seamanship 8vo,  *7  50 

Half  morocco *9  oo 

Knox,  W.  F.     Logarithm  Tables (In  Preparation.) 

Knott,  C.  G.,  and  Mackay,  J.  S.     Practical  Mathematics 8vo,  2  oo 

Koester,  F.     Steam-Electric  Power  Plants 4to,  *5  oo 

Hydroelectric  Developments  and  Engineering 4to,  *5  oo 

Koller,  T.     The  Utilization  of  Waste  Products 8vo,  *3  50 

Cosmetics 8vo,  *2  50 

Kretchmar,  K.     Yarn  and  Warp  Sizing , 8vo,  *4  oo 

Lambert,  T.     Lead  and  its  Compounds 8vo,  *3  50 

Bone  Products  and  Manures 8vo,  *3  oo 

Lamborn,  L.  L.     Cottonseed  Products 8vo,  *3  oo 

Modern  Soaps,  Candles,  and  Glycerin 8vo,  *7  50 

Lamprecht,  R.     Recovery  Work  After  Pit  Fires.     Trans,  by  C.  Salter .  .  8vo,  *4  oo 
Lanchester,  F.  W.     Aerial  Flight.     Two  Volumes.     8vo. 

Vol.   I.     Aerodynamics *6  oo 


D.   VAN  NOSTRAND   COMPANY'S  SHORJ1  TITLE  CATALOG      15 

Lanchester,  F.  W.  Aerial  Flight.  Vol.  II.  Aerodonetics *6  oo 

Larner,  E.  T.  Principles  of  Alternating  Currents i2mo,  *i  25 

Larrabee,  C.  S.  Cipher  and  Secret  Letter  and  Telegraphic  Code ithno,  o  60 

La  Rue,  B.  F.  Swing  Bridges.  (Science  Series  No.  107.) i6mo,  o  50 

Lassar-Cohn,  Dr.  Modern  Scientific  Chemistry.  Trans,  by  M.  M.  Patti- 

son  Muir i2mo,  *2  oo 

Latimer,  L.  H.,  Field,  C.  J.,  and  Howell,  J.  W.  Incandescent  Electric 

Lighting.  (Science  Series  No.  57.) i6mo,  o  50 

Latta,  M.  N.  Handbook  of  American  Gas-Engineering  Practice 8vo,  *4  50 

—  American  Producer  Gas  Practice 4to,  *6  oo 

Leask,  A.  R.     Breakdowns  at  Sea i2mo,  2  oo 

Refrigerating  Machinery I2mo,  2  oo 

Lecky,  S.  T.  S.     "  Wrinkles  "  in  Practical  Navigation 8vo,  *8  oo 

Le  Doux,  M.     Ice-Making  Machines.     (Science  Series  No.  46.) ....  i6mo,  o  50 

Leeds,  C.  C.     Mechanical  Drawing  foi  Trade  Schools oblong  4to, 

High  School  Edition *i  25 

Machinery  Trades  Edition *2  oo 

Lefe*vre,  L.     Architectural  Pottery.      Trans,  by  H.  K.  Bird  and  W.  M. 

Binns : 4to,  *7  50 

Lehner,  S.     Ink  Manufacture.     Trans,  by  A.  Morris  and  H.  Robson  . .  8vo,  *2  50 

Lemstrom,  S.     Electricity  in  Agriculture  and  Horticulture 8vo,  *i  50 

Le  VanfW.  B.     Steam-Engine  Indicator.     (Science  Series  No.  78.) .  i6mo,  o  50 

Lewes,  V.  B.     Liquid  and  Gaseous  Fuels.     (Westminster  Series.).  ..  .8vo,  *2  oo 

Lewis,  L.  P.    Railway  Signal  Engineering 8vo,  *3  50 

Lieber,  B.  F.     Lieber's  Standard  Telegraphic  Code 8vo,  *io  oo 

Code.     German  Edition 8vo,  *io  oo 

—  Spanish  Edition 8vo,  *io  oo 

French  Edition 8vo,  *io  oo 

—  Terminal  Index 8vo,  *2  50 

Lieber's  Appendix folio,  *i$  oo 

—  Handy  Tables 4to,  *2  50 

—  Bankers  and  Stockbrokers'  Code  and  Merchants  and  Shippers'  Blank 

Tables 8vo,  *is  oo 

100,000,000  Combination  Code 8vo,  *io  oo 

Engineering  Code 8vo,  *I2  50 

Li  verm  ore,  V.  P.,  and  Williams,  J.     How  to  Become  a  Competent  Motor- 
man I2mo,  *i  oo 

Livingstone,  R.     Design  and  Construction  of  Commutators 8vo,  *2  25 

Lobben,  P.     Machinists'  and  Draftsmen's  Handbook 8vo,  2  50 

Locke,  A.  G.  and  C.  G.     Manufacture  of  Sulphuric  Acid 8vo,  10  oo 

Lockwood,  T.  D.     Electricity,  Magnetism,  and  Electro-telegraph  ....  8vo,  2  50 

—  Electrical  Measurement  and  the  Galvanometer 12 mo,  i  50 

Lodge,  O.  J.     Elementary  Mechanics i2mo,  i  50 

—  Signalling  Across  Space  without  Wires 8vo,  *2  oo 

Lord,  R.  T.     Decorative  and  Fancy  Fabrics 8vo,  *3  50 

Loring,  A.  E.     A  Handbook  of  the  Electromagnetic  Telegraph i6mo,  o  50 

—  Handbook.     (Science  Series  No.  39.) i6mo,  o  50 

Loewenstein,  L.  C.,  and  Crissey,  C.  P.     Centrifugal  Pumps *4  50 

Lucke,  C.  E.     Gas  Engine  Design 8vo,  *3  oo 

Power  Plants:  their  Design,  Efficiency,  and  Power  Costs.     2  vols. 

(In  Preparation,) 


16     D.  VAN   NOSTRAND. COMPANY'S  SHORT  TITLE   CATALOG 

Lunge,  G.     Coal-tar  and  Ammonia.     Two  Volumes 8vot  *rs  oo> 

—  Manufacture  of  Sulphuric  Acid  and  Alkali.     Four  Volumes 8vo, 

Vol.     I.     Sulphuric  Acid.     In  two  parts *i5  oo 

Vol.    II.     Salt  Cake,  Hydrochloric  Acid  and  Leblanc  Soda.      In  two 

parts *T5  o» 

Vol.  III.     Ammonia  Soda *io  oo 

Vol.  IV.   Electrolytic  Methods (In  Press.) 

-  Technical  Chemists'  Handbook i2mo,  leather,     *3  50 

—  Technical  Methods  of  Chemical  Analysis.     Trans,  by  C.  A.  Keane. 
in  collaboration  with  the  corps  of  specialists. 

Vol.   I.     In  two  parts 8vo,  *is  oo 

Vol.  II.    In  two  parts 8vo,  *i8  oo 

Vol.  Ill (In  Preparation.) 

Lupton,  A.,  Parr,  G.  D.  A.,  and  Perkin,  H.     Electricity  as  Applied  to 

Mining 8vo,     *4  50 

Luquer,  L.  M.     Minerals  in  Rock  Sections 8vo,     *i  50 

Macewen,  H.  A.     Food  Inspection - 8vo,  *2  50 

Mackenzie,  N.  F.     Notes  on  Irrigation  Works 8vo,  *2  50 

Mackie,  J.     How  to  Make  a  Woolen  Mill  Pay 8vo,  *z  oo 

Mackrow,  C.     Naval  Architect's  and  Shipbuilder's  Pocket-book. 

i6mo,  leather,  *s  oo 

Maguire,  Wm.  R.     Domestic  Sanitary  Drainage  and  Plumbing 8vo,  4  oo 

Mallet,  A.     Compound  Engines.     Trans,  by  R.  R.  Buel.     (Science  Series 

No.  10.) i6mo, 

Mansfield,  A.  N.     Electro-magnets.     (Science  Series  No.  64.) i6mo,  o  50 

Marks,  E.  C.  R.     Construction  of  Cranes  and  Lifting  Machinery.  ...  i2mo>  *r  50 
Construction  and  Working  of  Pumps i2mo,  *r  50 

—  Manufacture  of  Iron  and  Steel  Tubes i2mo,  *z  oo 

Mechanical  Engineering  Materials i2mo,  *T  oo 

Marks,  G.  C.     Hydraulic  Power  Engineering 8vo,  3;  50 

—  Inventions,  Patents  and  Designs i2mo,  *r  oo 

Marlow,  T.  G.     Drying  Machinery  and  Practice 8yo,  *5  oo 

Marsh,  C.  F.     Concise  Treatise  on  Reinforced  Concrete 8vo,  *z  so 

Marsh,  C.  F.,  and  Dunn,  W.     Reinforced  Concrete 4to,  *5  oo 

Marsh,  C.  F.,  and  Dunn,  W.     Manual  of  Reinforced  Concrete  and  Con- 
crete Block  Construction i6mo,  morocco,  *z  50 

Marshall,  W.  J.,  and  Sankey,  H.  R.     Gas  Engines.     (Westminster  Series.) 

8vo,  *2  o» 

Martin.  G ,     Triumphs  and  Wonders  of  Modern  Chemistry 8voF  *z  oo 

Massie,  W.  W.,  and  Underbill,  C.  R.     Wireless  Telegraphy  and  Telephony. 

i2mo,  *r  oo 
Matheson,  D.     Australian  Saw-Miller's  Log  and  Timber  Ready  Reckoner. 

I2mo,  leather,  r  go 

Mathot,  R.  E.     Internal  Combustion  Engines.  .  .  . , 8vo,  *6  oo 

Maurice,  W.     Electric  Blasting  Apparatus  and  Explosives 8vo,  *s  9* 

—  Shot  Firer's  Guide 8vo,  *r  50 

Maxwell,  J.  C.     Matter  and  Motion.     (Science  Series  No.  36.) i6mo,  o  &> 

Maxwell,  W.  H.,  and  Brown,  J.  T.     Encyclopedia  of  Municipal  and  Sani- 
tary Engineering 4to,  *ro  oo 

Mayer,  A.  M.     Lecture  Notes  on  Physics 8vo,       2  oo 


IX   VAN   NOSTRAND   COMPANY'S  SHORT  TITLE   CATALOG      17 

McCullough,  R.  S.     Mechanical  Theory  of  Heat 8vo,  3  50 

Mclntosh,  J.  G.     Technology  of  Sugar 8vo,  *4  50 

Industrial  Alcohol 8vo,  *3  oo 

—  Manufacture  of  Varnishes  and  Kindred  Industries.     Three  Volumes. 
8vo. 

Vol.     I.     Oil  Crushing,  Refining  and  Boiling *3  50 

Vol.    II.     Varnish  Materials  and  Oil  Varnish  Making *4  oo 

Vol.  HI.     Spirit  Varnishes  and  Materials *4  5<> 

McKnight,  J.  D.,  and  Brown,  A.  W.     Marine  Multitubular  Boilers *i  50 

McMaster,  J.  B.     Bridge  and  Tunnel  Centres.     (Science  Series  No.  20.) 

i6mo,  o  50 

McMechen,  F.L.      Tests  for  Ores,  Minerals  and  Metals i2mo,  *i  oo 

Mclleill,  B.     McNeill's  Code 8vo,  *6  oo 

McPherson,  J.  A.     Water- works  Distribution 8vo,  2  50 

Melick,  C.  W.     Dairy  Laboratory  Guide i2mo,  *i  25 

Merck,  E.     Chemical  Reagents;  Their  Purity  and  Tests 8vo,  *i  50 

Merrirt,  Wm.  H.     Field  Testing  for  Gold  and  Silver i6mo,  leather,  i  50 

Meyer,  J.  G.  A.,  and  Pecker,  C.  G.     Mechanical  Drawing  and  Machine 

Design 4to,  5  oo 

Michell,  S.     Mine  Drainage 8vo,  10  oo 

Mierzinski,  S.     Waterproofing  of  Fabrics.     Trans,  by  A.  Morris  and  H. 

Robson 8vo,  *2  50 

Miller,  E.  H.     Quantitative  Analysis  for  Mining  Engineers 8vo,  *i  50 

Miller,  G.  A.     Determinants.     (Science  Series  No.  105.) i6mo, 

Milroy,  M.  E.  W.     Home  Lace-making I2mo,  *i  oo 

Minifie,  W.     Mechanical  Drawing 8vo,  *4  oo 

Mitchell,  C.  A.,  and  Prideaux,  R.  M.     Fibres  Used  in  Textile  and  Allied 

Industries 8vo,  *3  oo 

Modern  Meteorology i2mo,  i  50 

Monckton,  C.  C.  F.     Radiotelegraphy.     (Westminster  Series.) 8vo,  *2  oo 

Monteverde,  R.  D.     Vest  Pocket  Glossary  of  English-Spanish,  Spanish- 
English  Technical  Terms 64010,  leather,  *i  oo 

Moore,  E.  C.  S.     New  Tables  for  the  Complete  Solution  of  Ganguillet  and 

Kutter's  Formula 8vo,  *5  oo 

Morecroft,  J.  H.,  and  Hehre,  F.  W.     Short  Course  in  Electrical  Testing. 

8vo,  *i  50 

Moreing,  C.  A.,andNeal,  T.    New  General  and  Mining  Telegraph  Code,  8vo,  *s  oo 

Morgan,  A.  P.     Wireless  Telegraph  Apparatus  for  Amateurs I2mo,  *i  50 

Moses,  A.  J.     The  Characters  of  Crystals 8vo,  *2  oo 

Moses,  A.  J.,  and  Parsons,  C.  L.     Elements  of  Mineralogy 8vo,  *2  50 

Moss,  S.  A.  Elements  of  Gas  Engine  Design.  (Science  Series  No.i2i.)i6mo,  o  50 

-  The  Lay-out  of  Corliss  Valve  Gears.   (Science  Series  No.  119.).  i6mo,  o  50 

Kullin,  J.  P.     Modern  Moulding  and  Pattern-making i2mo,  2  50 

Munby,  A.  E.     Chemistry  and  Physics  of  Building  Materials.     (Westmin- 
ster Series.) 8vo,  *2  oo 

Murphy,  J.  G.     Practical  Mining i6mo,  i  oo 

Murray,  J.  A.     Soils  and  Manures.     (Westminster  Series.) Svo,  *2  oo 

Kaquet,  A.     Legal  Chemistry i2mo,  2  oo 

Basmith,  J.     The  Student's  Cotton  Spinning Svo,  3  oo 

Recent  Cotton  Mill  Construction i2mo,  2  oo 


18     D.  VAN   NOSTRAND   COMPANY'S   SHORT  TITLE   CATALOG 

Neave,  G.  B,.  and  Heilbron,  I.  M.     Identification  of  Organic  Compounds. 

i2mo,  *i  25 

Neilson,  R.  M.     Aeroplane  Patents 8vo,  *2  oo 

Nerz,  F.     Searchlights.     Trans,  by  C.  Rodgers 8vo,  *3  oo 

Nesbit,  A.  F.     Electricity  and  Magnetism (In  Preparation.) 

Neuberger,  H.,  and  Noalhat,  H.     Technology  of  Petroleum.     Trans,  by  J. 

G.  Mclntosh 8vo,  *io  oo 

Newall,  J.  W.     Drawing,  Sizing  and  Cutting  Bevel-gears 8vo,  i  50 

Nicol,  G.     Ship  Construction  and  Calculations 8vo,  *4  50 

Nipher,  F.  E.     Theory  of  Magnetic  Measurements i2mo,  i  oo 

Nisbet,  H.     Grammar  of  Textile  Design 8vo,  *3  oo 

Nolan,  H.     The  Telescope.     (Science  Series  No.  51.) i6mo,  o  50 

Noll,  A.     How  to  Wire  Buildings .  I2mo,  i  50 

Nugent,  E.     Treatise  on  Optics i2mo,  i  50 

O'Connor,  H.  The  Gas  Engineer's  Pocketbook i2mo,  leather,  3  50- 

Petrol  Air  Gas '. i2mo,  *o  75 

Ohm,  G.  S.,  and  Lockwood,  T.  D.  Galvanic  Circuit.  Translated  by 

William  Francis.  (Science  Series  No.  102.) i6mo,  o  50 

Olsen,  J.  C.  Text-book  of  Quantitative  Chemical  Analysis 8vo,  *4  oo 

Olsson,  A.  Motor  Control,  in  Turret  Turning  and  Gun  Elevating.  (U.  S. 

Navy  Electrical  Series,  No.  i.) i2mo,  paper,  *o  50 

Oudin,  M.  A.  Standard  Polyphase  Apparatus  and  Systems 8vo,  *3  oo 

Palaz,  A.     Industrial  Photometry.     Trans,  by  G.  W.  Patterson,  Jr. .  .  8vo,  *4  oo 

Pamely,  C.     Colliery  Manager's  Handbook 8vo,  *io  oo 

Parr,  G.  D.  A.     Electrical  Engineering  Measuring  Instruments 8vo,  *3  50 

Parry,  E.  J.     Chemistry  of  Essential  Oils  and  Artificial  Perfumes ....  8vo,  *5  oo 

—  Foods  and  Drugs.     Two  Volumes 8vo, 

Vol.    I.     Chemical  and  Microscopical  Analysis  of  Foods  and  Drugs.  *y  50 

Vol.  H.     Sale  of  Food  and  Drugs  Act *3  oo 

Parry,  E.  J.,  and  Coste,  J.  H.     Chemistry  of  Pigments 8vo,  *4  50 

Parry,  L.  A.     Risk  and  Dangers  of  Various  Occupations 8vo,  *3  oo 

Parshall,  H.  F.,  and  Hobart,  H.  M.     Armature  Windings 4to,  *7  50 

Electric  Railway  Engineering 4to,  *io  oo 

Parshall,  H.  F.,  and  Parry,  E.     Electrical  Equipment  of  Tramways.. .  .  (In  Press.) 

Parsons,  S.  J.     Malleable  Cast  Iron 8vo,  *2  50 

Partington,  J.  R.     Higher  Mathematics  for  Chemical  Students.  .i2mo,  *2  oo 

Passmore,  A.  C.     Technical  Terms  Used  in  Architecture 8vo,  *3  50 

Patterson,  D.     The  Color  Printing  of  Carpet  Yarns 8vo,  *3  50 

Color  Matching  on  Textiles 8vo,  *3  oo 

The  Science  of  Color  Mixing 8vo,  *3  oo 

Paulding,  C.  P.     Condensation  of  Steam  in  Covered  and  Bare  Pipes.  .8vo,  *2  oo 

-  Transmission  of  Heat  through  Cold-storage  Insulation i2mo,  *i  oo 

Peirce,  B.     System  of  Analytic  Mechanics 4to,  10  oo 

Pendred,  V.     The  Railway  Locomotive.     (Westminster  Series.) 8vo,  *2  oo 

Perkin,  F.  M.     Practical  Methods  of  Inorganic  Chemistry i2mo,  *i  oo 

Perrigo,  0.  E.     Change  Gear  Devices 8vo,  i  oo 

Perrine,  F.  A.  C.     Conductors  for  Electrical  Distribution 8vo,  *3  50 

Perry,  J.     Applied  Mechanics 8vo,  *2  50 

Petit,  G.     White  Lead  and  Zinc  White  Paints. . ,                    8vo,  *i  50 


D.  VAN  NOSTRAND   COMPANY'S  SHORT  TITLE   CATALOG      19 

Petit,  R.     How  to  Build  an  Aeroplane.     Trans,  by  T.  O'B.  Hubbard,  and 

J.  H.  Ledeboer 8vo,  *i  50 

Pettit,  Lieut.  J.  S.     Graphic  Processes.     (Science  Series  No.  76.) . . .  i6mo,  o  50 
Philbrick,  P.  H.     Beams  and  Girders.     (Science  Series  No.  88.) .  .  .  i6mo, 

Phillips,  J.     Engineering  Chemistry 8vo,  *4  50 

Gold  Assaying 8vo,  *2  50 

Dangerous  Goods 8vo,  3  50 

Phin,  J.     Seven  Follies  of  Science I2mo,  *i  25 

Pickworth,  C.  N.     The  Indicator  Handbook.     Two  Volumes. .  i2mo,  each,  i  50 

• Logarithms  for  Beginners I2mo,  boards,  o  50 

The  Slide  Rule i2mo,  i  oo 

Plattner's  Manual  of  Blow-pipe  Analysis.    Eighth  Edition,  revised.    Trans. 

by  H.  B.  Cornwall 8vo,  *4  oo 

Plympton,  G.  W.    The  Aneroid  Barometer.    (Science  Series  No.  35.)   i6mo,  o  50 
How  to  become  an  Engineer.      (Science  Series  No.  100.) i6mo,  o  50 

—  Van  Nostrand's  Table  Book.     (Science  Series  No.  104.) i6mo,  o  50 

Pochet,  M.  L.     Steam  Injectors.     Translated  from  the  French.     (Science 

Series  No.  29.) i6mo,  o  50 

Pocket  Logarithms  to  Four  Places.     (Science  Series  No.  65.) i6mo,  o  50 

leather,  i  oo 

Polleyn,  F.     Dressings  and  Finishings  for  Textile  Fabrics 8vo,  *3  oo 

Pope,  F.  L.     Modern  Practice  of  the  Electric  Telegraph 8vo,  i  50 

Popplewell,  W.  C.  Elementary  Treatise  on  Heat  and  Heat  Engines. .  I2mo,  *3  oo 
Prevention  of  Smoke 8vo,  *3  50 

-  Strength  of  Materials 8vo,  *i  75 

Potter,  T.     Concrete 8vo,  *3  oo 

Practical  Compounding  of  Oils,  Tallow  and  Grease 8vo,  *3  50 

Practical  Iron  Founding i2mo,  i  50 

Pray,  T.,  Jr.     Twenty  Years  with  the  Indicator 8vo,  2  50 

—  Steam  Tables  and  Engine  Constant 8vo,  2  oo 

—  Calorimeter  Tables 8vo,  i  oo 

Preece,  W.  H.     Electric  Lamps (In  Press.) 

Prelini,  C.     Earth  and  Rock  Excavation 8vo,  *3  oo 

—  Graphical  Determination  of  Earth  Slopes 8vo,  *2  oo 

-  Tunneling.     New  Edition 8vo,  *3  oo 

—  Dredging.    A  Practical  Treatise 8vo,  *3  oo 

Prescott,  A.  B.     Organic  Analysis 8vo,  5  oo 

Prescott,  A.  B.,  and  Johnson,  0.  C.     Qualitative  Chemical  Analysis.  .  .8vo,  *3  50 
Prescott,  A.  B.,  and  Sullivan,  E.  C.     First  Book  in  Qualitative  Chemistry. 

I2mo,  *i  50 

Pritchard,  0.  G.     The  Manufacture  of  Electric-light  Carbons .  .  8vo,  paper,  *o  60 
Pullen,  W.  W.  F.     Application  of  Graphic  Methods  to  the  Design  of 

Structures i2mo,  *2  50 

—  Injectors:  Theory,  Construction  and  Working _  i2mo,  *i  50 

Pulsifer,  W.  H.     Notes  for  a  History  of  Lead 8vo,  4  oo 

Purchase,  W.  R.     Masonry i2mo,  *3  oo 

Putsch,  A.     Gas  and  Coal-dust  Firing 8vo,  *3  oo 

Pynchon,  T.  R.     Introduction  to  Chemical  Physics 8vo,  3  oo 

Rafter  G.  W.     Mechanics  of  Ventilation.     (Science  Series  No.  33.) .  i6mo,  o  50 

—  Potable  Water,     (Science  Series  No.  103.) i6mo,  o  50 


20      D    VAN   NOSTRAND  COMPANY'S  SHORT  TITLE  CATALOG 

Rafter,  G.  W.     Treatment  of  Septic  Sewage.     (Science  Series  No.  118.) 

i6mo,  o  50 

Rafter,  G.  W.,  and  Baker,  M.  N.     Sewage  Disposal  in  the  United  States .  4to,  *6  oo 

Raikes,  H.  P.     Sewage  Disposal  Works 8vo,  *4  oo 

Railway  Shop  Up-to-Date 4to,  2  oo 

Ramp,  H.  M.     Foundry  Practice (In  Press.) 

Randall,  P.  M.     Quartz  Operator's  Handbook i2mo,  2  oo 

Randau,  P.     Enamels  and  Enamelling : 8vo,  *4  oo 

Rankine,  W.  J.  M.     Applied  Mechanics 8vo,  5  oo 

Civil  Engineering 8vo,  6  50 

Machinery  and  Millwork 8vo,  5  oo 

The  Steam-engine  and  Other  Prime  Movers .8vo,  5  oo 

Useful  Rules  and  Tables 8vo,  4  oo 

Rankine,  W.  J.  M.,  and  Bamber,  E.  F.     A  Mechanical  Text-book 8vo,  3  50 

Raphael,  F.  C.     Localization  of  Faults  in  Electric  Light  and  Power  Mains. 

8vo,  *3  oo 

Rathbone,  R.  L.  B.     Simple  Jewellery 8vo,  *2  oo 

Rateau,  A.     Flow  of  Steam  through  Nozzles  and  Orifices.     Trans,  by  H. 

B.  Brydon 8vo,  *i  50 

Rausenberger,  F.     The  Theory  of  the  Recoil  of  Guns 8vo,  *4  50 

Rautenstrauch,  W.     Notes  on  the  Elements  of  Machine  Design. 8 vo,  boards,  *i  50 
Rautenstrauch,  W.,  and  Williams,  J.  T.     Machine  Drafting  and  Empirical 
Design. 

Part   I.  Machine  Drafting 8vo,  *i  25 

Part  II.  Empirical  Design (In  Preparation.) 

Raymond,  E.  B.     Alternating  Current  Engineering i2mo,  *2  50 

Rayner,  H.     Silk  Throwing  and  Waste  Silk  Spinning 8vo,  *2  50 

Recipes  for  the  Color,  Paint,  Varnish,  Oil,  Soap  and  Drysaltery  Trades .  8vo,  *3  50 

Recipes  for  Flint  Glass  Making i2mo,  *4  50 

Redwood,  B.     Petroleum.     (Science  Series  No.  92.) i6mo,  o  50 

Reed's  Engineers'  Handbook 8vo,  *5  oo 

Key  to  the  Nineteenth  Edition  of  Reed's  Engineers'  Handbook .  .  8vo,  *3  oo 

Useful  Hints  to  Sea-going  Engineers i2mo,  i  50 

Marine  Boilers 121110,  2  oo 

Reinhardt,  C.  W.     Lettering  for  Draftsmen,  Engineers,  and  Students. 

oblong  4to,  boards,  i  oo 

The  Technic  of  Mechanical  Drafting oblong  4to,  boards,  *i  oo 

Reiser,  F.     Hardening  and  Tempering  of  Steel.     Trans,  by  A.  Morris  and 

H.  Robson i2mo,  *2  05 

Reiser,  N.     Faults  in  the  Manufacture  of  Woolen  Goods.     Trans,  by  A. 

Morris  and  H.  Robson 8vo,  *2  50 

Spinning  and  Weaving  Calculations 8vo,  *5  oo 

Renwick,  W.  G.     Marble  and  Marble  Working 8vo,  5  oo 

Reynolds,   0.,   and  Idell,   F.   E.     Triple   Expansion   Engines.     (Science 

Series  No.  99.) i6mo,  o  50 

Rhead,  G.  F.     Simple  Structural  Woodwork i2mo,  *i  oo 

Rice,  J.  M.,  and  Johnson,  W.  W.     A  New  Method  of  Obtaining  the  Differ- 
ential of  Functions i2mo,  o  50 

Richardson,  J.     The  Modern  Steam  Engine 8vo,  *3  50 

Richardson,  S.  S.     Magnetism  and  Electricity i2mo,  *2  oo 

Rideal,  S.     Glue  and  Glue  Testing 8vo,  *4  oo 


D.   VAN   NOSTRAND   COMPANY'S  SHORT  TITLE  CATALOG     21 

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Ripper,  W.     Course  of  Instruction  in  Machine  Drawing folio,  *6  oo 

Roberts,  F.  C.     Figure  of  the  Earth.     (Science  Series  No.  79.) i6mo,  o  50 

Roberts,  J.,  Jr.     Laboratory  Work  in  Electrical  Engineering 8vo,  *2  oo 

Robertson,  L.  S.     Water-tube  Boilers 8vo,  3  oo 

Robinson,  J.  B.     Architectural  Composition 8vo,  *2  50 

Robinson,  S.  W.     Practical  Treatise  on  the  Teeth  of  Wheels.     (Science 

Series  No.  24.) i6mo,  o  50 

Railroad  Economics.     (Science  Series  No.  59.) i6mo,  o  50 

Wrought  Iron  Bridge  Members.     (Science  Series  No.  60.) i6mo,  o  50 

Robson,  J.  H.     Machine  Drawing  and  Sketching 8vo,  *i  50 

Roebling,  J   A.     Long  and  Short  Span  Railway  Bridges folio,  25  oo 

Rogers,  A.     A  Laboratory  Guide  of  Industrial  Chemistry 12 mo,  *i  50 

Rogers,  A.,  and  Aubert,  A.  B.     Industrial  Chemistry (In  Press.) 

Rogers,  F.     Magnetism  of  Iron  Vessels.     (Science  Series  No.  30.) .  .  i6mo,  o  50 

Rollins,  W.     Notes  on  X-Light 8vo,  *5  oo 

Rose,  J.     The  Pattern-makers'  Assistant 8vo,  2  50 

—  Key  to  Engines  and  Engine-running i2mo,  2  50 

Rose,  T.  K.     The  Precious  Metals.     (Westminster  Series.) 8vo,  *2  oo 

Rosenhain,  W.     Glass  Manufacture.     (Westminster  Series.) .8vo,  *2  oo 

Ross,  W.  A.     Plowpipe  in  Chemistry  and  Metallurgy i2mo,  *2  oo 

Rossiter,  J.  T.     Steam  Engines.     (Westminster  Series.). .  .  .8vo  (In  Press.) 

Pumps  and  Pumping  Machinery.     (Westminster  Series.).. 8vo  (In  Press.) 

Roth.     Physical  Chemistry 8vo,  *2  oo 

Rouillion,  L.     The  Economics  of  Manual  Training 8vo,  2  oo 

Rowan,  F.  J.     Practical  Physics  of  the  Modern  Steam-boiler 8vo,  7  50 

Rowan,   F.   J.,   and  Idell,   F.   E.     Boiler  Incrustation  and  Corrosion. 

(Science  Series  No.  27.) i6mo,  o  50 

Roxburgh,  W.     General  Foundry  Practice 8vo,  *3   50 

Ruhmer,  E.     Wireless  Telephony.     Trans,  by  J.  Erskine-Murray .  .  .  .8vo,  *3  50 

Russell,  A.     Theory  of  Electric  Cables  and  Networks 8vo,  *3  oo 

Sabine,  R.     History  and  Progress  of  the  Electric  Telegraph ....  i2mo,  i  25 

Saeltzer  A.     Treatise  on  Acoustics i2mo,  i  oo 

Salomons,  D.     Electric  Light  Installations.     i2mo. 

Vol.    I.     The  Management  of  Accumulators 2  50 

Vol.  II.     Apparatus 2  25 

Vol.  III.     Applications i  50 

Sanford,  P.  G.     Nitro-explosives 8vo,  *4  oo 

Saunders,  C.  H.     Handbook  of  Practical  Mechanics i6mo,  i  oo 

leather,  i  25 

Saunnier,  C.     Watchmaker's  Handbook i2mo,  3  oo 

Sayers,  H.  M.     Brakes  for  Tram  Cars 8vo,  *i  25 

Scheele,  C.  W.     Chemical  Essays 8vo,  *2  oo 

Schellen,  H.     Magneto-electric  and  Dynamo-electric  Machines 8vo,  5  oo 

Scherer,  R.     Casein.     Trans,  by  C.  Salter 8vo,  *3  oo 

Schidrowitz,  P.     Rubber,  Its  Production  and  Industrial  Uses 8vo,  *5  oo 

Schmall,  C.  N.     First  Course  in  Analytic  Geometry,  Plane  and  Solid. 

izmo,  half  leather,  *r  75 

Schmall,  C.  N.,  and  Shack,  S.  M.     Elements  of  Plane  Geometry.  .  .  .  i2mo,  *i  25 

Schmeer,  L.     Flow  of  Water 8vo,  *3  oo 


22      D.   VAN   NOSTRAND   COMPANY'S  SHORT  TITLE  CATALOG 

Schumann,  F.     A  Manual  of  Heating  and  Ventilation i2mo,  leather,  i  50 

Schwarz,  E.  H.  L.     Causal  Geology 8vo,  *2  50 

Schweizer,  V.,  Distillation  of  Resins 8vo,  *3  50 

Scott,  W.  W.     Qualitative  Analysis.     A  Laboratory  Manual 8vo,  *i  50 

Scribner,  J.  M.     Engineers'  and  Mechanics'  Companion  .  . .  i6mo,  leather,  i  50 

Searle,  A.  B.     Modern  Brickmaking 8vo,  *5  oo 

Searle,  G.  M.     "  Sumners'  Method."     Condensed  and  Improved.    (Science 

Series  No.  124.) i6mo,  o  50 

Seaton,  A.  E.     Manual  of  Marine  Engineering 8vo,  •  6  oo 

Seaton,  A.  E.,  and  Rounthwaite,  H.  M.     Pocket-book  of  Marine  Engineer- 
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Seeligmann,  T.,  Torrilhon,  G.  L.,  and  Falconnet,  H.     India  Rubber  and 

Gutta  Percha.     Trans,  by  J.  G.  Mclntosh 8vo,  *5  oo 

Seidell,  A.     Solubilities  of  Inorganic  and  Organic  Substances ........  8vo,  *3  oo 

Sellew,  W.  H.     Steel  Rails 4to  (In  Press.) 

Senter,  G.     Outlines  of  Physical  Chemistry I2mo,  *i  75 

Sever,  G.  F.     Electric  Engineering  Experiments 8vo,  boards,  *i  oo 

Sever,  G.  F.,  and  Townsend,  F.     Laboratory  and  Factory  Tests  in  Electrical 

Engineering 8vo,  *2  50 

Sewall,  C.  H.     Wireless  Telegraphy 8vo,  *2  oo 

Lessons  in  Telegraphy i2mo,  *i  oo 

Sewell,  T.     Elements  of  Electrical  Engineering 8vo,  *3  oo 

—  The  Construction  of  Dynamos 8vo,  *3  oo 

Sexton,  A.  H.     Fuel  and  Refractory  Materials i2mo,  *2  50 

—  Chemistry  of  the  Materials  of  Engineering i2mo,  *2  50 

—  Alloys  (Non-Ferrous) gvo,  *3  oo 

—  The  Metallurgy  of  Iron  and  Steel 8vo,  *6  50 

Seymour,  A.     Practical  Lithography 8vo,  *2  50 

—  Modern  Printing  Inks 8vo,  *2  oo 

Shaw,  Henry  S.  H.     Mechanical  Integrators.     (Science  Series  No.  83.) 

i6mo,  o  50 

Shaw,  P.  E.     Course  of  Practical  Magnetism  and  Electricity 8vo,  *i  oo 

Shaw,  S.     History  of  the  Staffordshire  Potteries 8vo,  *3  oo 

Chemistry  of  Compounds  Used  in  Porcelain  Manufacture 8vo,  *5  oo 

Shaw,  W.  N.      Forecasting  Weather 8vo  (In  Press.) 

Sheldon,  S.,  and  Hausmann,  E.     Electric  Traction i2mo,  *2  50 

Direct  Current  Machines i2mo,  *2  50 

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Sherriff,  F.  F.     Oil  Merchants'  Manual I2mo,  *3  50 

Shields,  J.  E.     Notes  on  Engineering  Construction I2mo,  i  50 

Shock,  W.  H.     Steam  Boilers 4to,  half  morocco,  15  oo 

Shreve,  S.  H.     Strength  of  Bridges  and  Roofs 8vo,  3  50 

Shunk,  W.  F.     The  Field  Engineer i2mo,  morocco,  2  50 

Simmons,  W.  H.,  and  Appleton,  H.  A.    Handbook  of  Soap  Manufacture. 

8vo,  *3  oo 

Simmons,  W.  H.,  and  Mitchell,  C.  A.     Edible  Fats  and  Oils 8vo,  *3  oo 

Simms,  F.  W.     The  Principles  and  Practice  of  Leveling 8vo,  2  oo 

—  Practical  Tunneling 8vo,  7  50 

Simpson,  G.     The  Naval  Constructor i2mo,  morocco,  *5  oo 

Sinclair,  A.     Development  of  the  Locomotive  Engine  .  . .  8vo,  half  leather,  5  oo 


D.  VAN   NOSTRAND   COMPANY'S   SHORT  TITLE  CATALOG     23 

Sinclair,  A.     Twentieth  Century  Locomotive 8vo,  half  leather,  *s  oo 

Sindall,  R.  W.     Manufacture  of  Paper.     (Westminster  Series.) 8vo,  *2  oo 

Sloane,  T.  O'C.     Elementary  Electrical  Calculations i2mo,  *2  oo 

Smith,  C.  A.  M.     Handbook  of  Testing,  MATERIALS.  ...f 8vo,  *2  50 

Smith,  C.  A.  M.,  and  Warren,  A.  G.     New  Steam  Tables 8vo, 

Smith,  C.  F.     Practical  Alternating  Currents  and  Testing 8vo,  *2  50 

Practical  Testing  of  Dynamos  and  Motors 8vo,  *2  oo 

Smith,  F.  E.     Handbook  of  General  Instruction  for  Mechanics.  .  .  .  i2mo,  i  50 

Smith,  J.  C.     Manufacture  of  Paint 8vo,  *3  oo 

Smith,  R.  H.     Principles  of  Machine  Work i2mo,  *3  oo 

—  Elements  of  Machine  Work i2mo,  *2  oo 

Smith,  W.     Chemistry  of  Hat  Manufacturing i2mo,  *3  oo 

Snell,  A.  T.     Electric  Motive  Power 8vo,  *4  oo 

Snow,  W.  G.     Pocketbook  of  Steam  Heating  and  Ventilation.    (In  Press.) 
Snow,  W.  G.,  and  Nolan,  T.     Ventilation  of  Buildings.     (Science  Series 

No.  5.) i6mo,  o  50 

Soddy,  F.     Radioactivity.     8vo,  *3  oo 

Solomon,  M.     Electric  Lamps.     (Westminster  Series.) 8vo,  *2  oo 

Sothern,  J.  W.     The  Marine  Steam  Turbine 8vo,  *5  oo 

Soxhlet,  D.  H.     Dyeing  and  Staining  Marble.     Trans,  by  A.  Morris  and 

H.  Robson 8vo,  *2  50 

Spang,  H.  W.     A  Practical  Treatise  on  Lightning  Protection i2mo,  i  oo 

Spangenburg,    L.     Fatigue    of   Metals.     Translated    by    S.    H.    Shreve. 

(Science  Series  No.  23.) i6mo,  o  50 

Specht,  G.  J.,  Hardy,  A.  S.,  McMaster,  J.B  .,  and  Walling.     Topographical 

Surveying.     (Science  Series  No.  72.) i6mo,  o  50 

Speyers,  C.  L.     Teft-book  of  Physical  Chemistry 8vo,  *2  25 

Stahl,  A.  W.     Transmission  of  Power.     (Science  Series  No.  28.) . .  .  i6mo, 

Stahl,  A.  W.,  and  Woods,  A.  T.     Elementary  Mechanism i2mo,  *2  oo 

Staley,  C.,  and  Pierson,  G.  S.     The  Separate  System  of  Sewerage.  .  .  .8vo,  *3  oo 

Standage,  H.  C.     Leatherworkers'  Manual .8vo,  *3  50 

Sealing  Waxes,  Wafers,  and  Other  Adhesives 8vo,  *2  oo 

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Stansbie,  J.  H.     Iron  and  Steel.     (Westminster  Series.) 8vo,  *2  oo 

Steinman,  D.  B.     Suspension  Bridges  and  Cantilevers.     (Science  Series 

No.  127) o  50 

Stevens,  H.  P.     Paper  Mill  Chemist i6mo,  *2  50 

Stevenson,  J.  L.     Blast-Furnace  Calculations I2mo,  leather,  *2  oo 

Stewart,  A.     Modern  Polyphase  Machinery i2mo,  *2  oo 

Stewart,  G.     Modern  Steam  Traps i2mo,  *i  25 

Stiles,  A.     Tables  for  Field  Engineers i2mo,  i  oo 

Stillman,  P.     Steam-engine  Indicator i2mo,  i  oo 

Stodola,  A.     Steam  Turbines.     Trans,  by  L.  C.  Loewenstein 8vo,  *5  oo 

Stone,  H.     The  Timbers  of  Commerce 8vo,  3  50 

Stone,  Gen.  R.    New  Roads  and  Road  Laws i2mo,  i  oo 

Stopes,  M.     Ancient  Plants 8vo,  *2  oo 

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Sudborough,  J.  J.,  and  James,  T.  C.     Practical  Organic  Chemistry.  .  i2mo,  *2  oo 

Suffling,  E.  R.     Treatise  on  the  Art  of  Glass  Painting 8vo,  *3  50 

Swan,  K.     Patents,  Designs  and  Trade  Marks.      (Westminster  Series. ).8vo,  *2  oo 

Sweet,  S.  H.     Special  Report  on  Coal 8vo,  3  oo 


24     D.  VAN   NOSTRAND   COMPANY'S   SHORT  TITLE   CATALOG 

Swinburne,  J.,  Wordingham,  C.  H.,  and  Martin,  T.  C.     Eletcric  Currents. 

(Science  Series  No.  109.) i6mo,  o  50 

Swoope,  C.  W.     Practical  Lessons  in  Electricity i2mo,  *2  oo 

Tailfer,  L.     Bleaching  linen  and  Cotton  Yarn  and  Fabrics 8vo,  *5  oo 

Tate,  J.  S.     Surcharged  and  Different  Forms  of  Retaining-walls.     (Science 

Series  No.  7.) i6mo, 

Templeton,  W.     Practical  Mechanic's  Workshop  Companion. 

i2mo,  morocco,  2  oo 
Terry,  H.  L.     India  Rubber  and  its  Manufacture.     (Westminster  Series.) 

8vo,  *2  oo 

Thayer,  H.  R.     Design  of  Structures (In  Press.) 

Thiess,  J.  B.  and  Joy,  G.  A.     Toll  Telephone  Practice (In  Press.) 

Thorn,  C.,  and  Jones,  W.  H.     Telegraphic  Connections oblong  i2mo,  i  50 

Thomas,  C.  W.     Paper-makers'  Handbook (In  Press.) 

Thompson,  A.  B.     Oil  Fields  of  Russia 4to,  *7  50 

—  Petroleum  Mining  and  Oil  Field  Development 8vo,  *5  oo 

Thompson,  E.  P.     How  to  Make  Inventions 8vo,  o  50 

Thompson,  S.  P.     Dynamo  Electric  Machines.     (Science  Series  No.  75.) 

i6mo,  o  50 

Thompson,  W.  P.     Handbook  of  Patent  Law  of  All  Countries i6mo,  i  50 

Thornley,  T.     Cotton  Combing  Machines 8vo,  *3  oo 

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First  Year *i  50 

Second  Year *2  50 

Third  Year ." *2  50 

Thurso,  J.  W.     Modern  Turbine  Practice % 8vo,  *4  oo 

Tidy,  C.   Meymott.     Treatment  of  Sewage.     (Science  Series  No.   94.). 

i6mo,  o  50 

Tinney,  W.  H.     Gold-mining  Machinery 8vo,  *3  oo 

Titherley,  A.  W.     Laboratory  Course  of  Organic  Chemistry 8vo,  *2  oo 

Toch,  M.     Chemistry  and  Technology  of  Mixed  Paints 8vo,  *3  oo 

Materials  for  Permanent  Painting i2mo,  *2  oo 

Todd,  J.,  and  Whall,  W.  B.     Practical  Seamanship 8vo,  *7  50 

Tonge,  J.     Coal.     (Westminster  Series.) 8vo,  *2  oo 

Townsend,  F.     Alternating  Current  Engineering 8vo,  boards  *o  75 

Townsend,  J.     lonization  of  Gases  by  Collision 8vo,  *i  25 

Transactions  of  the  American  Institute  of  Chemical  Engineers.     8vo. 

Vol.      I.     1908.. * *6  oo 

Vol.    II.     1909 *6  oo 

Vol.  III.      1910 *6  oo 

Traverse  Tables.     (Science  Series  No.  115.) i6mo,  o  50 

morocco,  i  oo 
Trinks,  W.,  and  Housum,  C.     Shaft  Governors.    "{Science  Series  No.  122.) 

i6mo,  o  50 

Trowbridge,  W.  P.     Turbine  Wheels.     (Science  Series  No.  44.) i6mo,  o  50 

Tucker,  J.  H.     A  Manual  of  Sugar  Analysis 8vo,  3  50 

Tumlirz,  0.     Potential.     Trans,  by  D.  Robertson i2mo,  i  25 

Tunner,  P.  A.     Treatise  on  Roll-turning.     Trans,  by  J.  B.  Pearse. 

8vo,  text  and  folio  atlas,  10  oo 

Turbayne,  A.  A.     Alphabets  and  Numerals 4to,  2  oo 


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Turnbull,  Jr.,  J.,  and  Robinson,  S.  W.     A  Treatise  on  the  Compound 

Steam-engine,      (Science  Series  No.  8.) i6mo, 

Turrill,  S.  M.     Elementary  Course  in  Perspective i2mo,  *i  25 

Underbill,  C.  R.     Solenoids,  Electromagnets  and  Electromagnetic  Wind- 
ings  I2H10,  *2    00 

Urquhart,  J.  W.     Electric  Light  Fitting i2mo,  2   DO 

—  Electro-plating i2mo,  2  oo 

—  Electrotyping ( i2mo,  2  oo 

—  Electric  Ship  Lighting I2mo,  3  oo 

Universal  Telegraph  Cipher  Code i2mo,  i  oo 

Vacher,  F.     Food  Inspector's  Handbook I2mo,  *2  50 

Van  Nostrand's  Chemical  Annual.     Second  issue  1909 12mo,  *2  50 

—  Year  Book  of  Mechanical  Engineering  Data.    First  issue  1912 .  . .  (In  Press.) 

Van  Wagenen,  T.  F.     Manual  of  Hydraulic  Mining i6mo,  i  oo 

Vega,  Baron  Von.     Logarithmic  Tables 8vo,  half  morocco,  2  50 

Villon,  A.  M.     Practical  Treatise  on  the  Leather  Industry.     Trans,  by  F. 

T.  Addyman 8vo,  *io  oo 

Vincent,  C.  Ammonia  and  its  Compounds.  Trans,  by  M.  J.  Salter ..  8vo,  *2  oo 

Volk,  C.  Haulage  and  Winding  Appliances 8vo,  *4  oo 

Von  Georgievics,  G.  Chemical  Technology  of  Textile  Fibres.  Trans,  by 

C.  Salter 8vo,  *4  50 

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Vose,  G.  L.     Graphic  Method  for  Solving  Certain  Questions  in  Arithmetic 

and  Algebra.     (Science  Series  No.  16.) i6mo,  o  50 

Wabner,  R.     Ventilation  in  Mines.     Trans,  by  C.  Salter 8vo,  *4  50 

Wade,  E.  J.     Secondary  Batteries 8vo,  *4  oo 

Wadsworth,  C.     Primary  Battery  Ignition i2mo  (In  Press.) 

Wagner,  E.     Preserving  Fruits,  Vegetables,  and  Meat i2mo,  *2  50 

Walker,  F.     Aerial  Navigation 8vo,  2  oo 

—  Dynamo  Building.     (Science  Series  No.  98.) i6mo,  o  50 

—  Electric  Lighting  for  Marine  Engineers 8vo,  2  oo 

Walker,  S.  F.     Steam  Boilers,  Engines  and  Turbines 8vo,  3  oo 

Refrigeration,  Heating  and  Ventilation  on  Shipboard I2mo,  *2  oo 

— Electricity  in  Mining 8vo,  *3  50 

Walker,  W.  H.     Screw  Propulsion. 8vo,  o  75 

Wallis-Tayler,  A.  J.     Bearings  and  Lubrication 8vo,  *i  50 

—  Modern  Cycles 8vo,  4  oo 

—  Motor  Cars 8vo,  i  80 

Wallis-Tayler,  A.  J.     Motor  Vehicles  for  Business  Purposes 8vo,  3  50 

—  Pocket  Book  of  Refrigeration  and  Ice  Making I2mo,  i  50 

—  Refrigeration,  Cold  Storage  and  Ice-Making 8vo, 

—  Sugar  Machinery 12010,  *2  oo 

Wanklyn,  J.  A.     Water  Analysis. i2mo,  2  oo 

Wansbrough,  W.  D.     The  A  B  C  of  the  Differential  Calculus i2mo,  *i  50 

—  Slide  Valves I2mo,  *2  oo 

Ward,  J.  H.     Steam  for  the  Million 8vo,  i  oo 

Waring,  Jr.,  G.  E.     Sanitary  Conditions.     (Science  Series  No.  31.). .  i6mo,  o  50 

—  Sewerage  and  Land  Drainage *6  oo 


26     D.  VAN   NOSTRAND   COMPANY'S   SHORT  TITLE  CATALOG 

Waring,  Jr.,  G.  E.     Modern  Methods  of  Sewage  Disposal i2mo,  2  oo 

How  to  Drain  a  House i2mo,  i  25 

Warren,  F.  D.     Handbook  on  Reinforced  Concrete i2mo,  *2  50 

Watkins,  A.     Photography.     (Westminster  Series.) 8vo,  *2  oo 

Watson,  E.  P.     Small  Engines  and  Boilers I2mo,  i  25 

Watt,  A.     Electro-plating  and  Electro-refining  of  Metals 8vo,  *4  50 

—  Electro-metallurgy i2mo,  i  oo 

—  The  Art  of  Soap-making 8vo,  3  oo 

—  Leather  Manufacture 8vo,  *4  oo 

—  Paper-Making 8vo,  3  oo 

Weale,  J.     Dictionary  of  Terms  Used  in  Architecture i2mo,  2  50 

Weale's  Scientific  and  Technical  Series.     (Complete  list  sent  on  applica- 
tion.) 

Weather  and  Weather  Instruments i2mo,  i  oo 

paper,  o  50 

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Webber,  W.  H.  Y.     Town  Gas.     (Westminster  Series.) 8vo,  *2  oo 

Weisbach,  J.     A  Manual  of  Theoretical  Mechanics 8vo,  *6  oo 

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Wilcox,  R.  M.     Cantilever  Bridges.     (Science  Series  No.  25.) i6mo,  o  50 

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Winchell,  K.  H.,  and  A.  N.     Elements  of  Optical  Mineralogy 8vo,  *3  50 

Winkler,  C.,  and  Lunge,  G.     Handbook  of  Technical  Gas- Analysis. .  .8vo,  4  oo 

Winslow,  A.     Stadia  Surveying.     (Science  Series  No.  77.) i6mo,  o  50 

Wisser,   Lieut.   J.   P.     Explosive  Materials.     (Science   Series  No.   70.). 

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Wood,  De  V.     Luminiferous  Aether.     (Science  Series  No.  85.) ....  i6mo,  o  50 
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ELECTRICAL  ENGINEER'S 
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1,400  Pages  500  Tables  1,100  Illustrations 


1U 


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